![[Feedback]](/icons/banner/feedbackACT.gif){kind=icon}
![[For Subscribers]](/icons/banner/subscriberACT.gif){kind=icon}
![[Archive]](/icons/banner/archiveACT.gif){kind=icon}
![[Search]](/icons/banner/searchACT.gif){kind=icon}
![[Contents]](/icons/banner/tocACT.gif){kind=icon}
Previous Article | Next Article 
Molecular and Cellular Biology, August 2002, p. 5479-5491, Vol. 22, No. 15
0270-7306/02/$04.00+0 DOI: 10.1128/MCB.22.15.5479-5491.2002
Copyright © 2002, American Society for Microbiology. All Rights Reserved.
Department of Immunology, University of Manitoba, Winnipeg, Manitoba, Canada R3E 0W3,1 Department of Medicine, University of British Columbia and Vancouver Hospital, Jack Bell Research Centre, Vancouver, British Columbia, Canada V6H 3Z62
Received 8 October 2001/ Returned for modification 26 November 2001/ Accepted 30 April 2002
 |
ABSTRACT |
|---|
 Top Abstract IntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
|
INTRODUCTION |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
The importance of the PI3K pathway in B-lymphocyte activation and differentiation responses is well established. Studies examining the effects of PI3K inhibitors on B-cell responses in vitro indicate that PI3K is involved in CD40-induced immunoglobulin secretion in human B cells (1) and lipopolysaccharide (LPS)-induced proliferation in murine B cells (57). Human B cells pretreated with the PI3K inhibitor wortmannin show reduced anti-immunoglobulin M (anti-IgM)-induced thymidine incorporation and increased apoptosis, suggesting that PI3K-dependent signaling events deliver a critical component of survival and mitogenic signaling through the BCR. Studies examining mice deficient in the PI3K p85
subunit (15, 48) have demonstrated that PI3K activity is involved in both early B-cell differentiation and B-cell activation. p85-deficient B cells show impaired proliferation in response to anti-IgM, anti-CD40, interleukin 4, or LPS, suggesting that PI3K is required for mitogenic responses through a variety of activating receptors on B cells. Underlining the functional importance of the PI3K pathway in B cells is the fact that it is subject to negative regulation by the inhibitory Fc receptor Fc
RII (37, 49). FcRII is a physiologically important regulator of B-cell responses to antigens, since coligation of FcRII inhibits B-cell antigen receptor (BCR)-induced Ca2+ mobilization (9) and proliferation (37), and FcRII-deficient mice show exaggerated antibody responses (49). At least some aspects of FcRII-mediated inhibition of BCR signal transduction appear to be mediated by SHIP (6, 36); SHIP specifically antagonizes PIP3 generation by removing the 5-phosphate from PIP3 to generate the lipid product PI(3,4)P2 (11, 29). The importance of SHIP in regulating B-cell activation is supported by studies of SHIP-deficient cell lines and mice, which have defects in B-cell maturation and exaggerated BCR signaling responses (21, 36).
Given the importance of PI3K and SHIP in B-cell activation, a current, critical question is, what are the targets of 3-phosphoinositide second messengers in B cells and how do they function to regulate B-cell activation and differentiation? Two PH domain-containing targets of PI3K are known to be activated by the BCR: the Tec family protein tyrosine kinase Bruton's tyrosine kinase (Btk) (41, 42) and the serine/threonine kinase Akt (2, 5, 10, 20). We have recently identified and characterized Bam32, a novel PH domain-containing protein that is recruited to the plasma membrane of activated B lymphocytes in a PI3K-dependent manner (31). Here we report the characterization of TAPP1 and TAPP2, two PH domain-containing adaptor proteins related to Bam32 that have recently been shown to bind specifically to PI(3,4)P2 (12). We demonstrate that these proteins represent targets of activated PI3K and are recruited to the plasma membranes of B lymphocytes in a sustained fashion after activation through the BCR.
|
MATERIALS AND METHODS |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
|
Plasmid constructs and antibodies.
Vectors encoding mouse TAPP2 and human TAPP1 fused to enhanced green fluorescent protein (EGFP) at their N termini were constructed by cloning the entire coding sequences into pEGFP-C1 (Clontech). C-terminal PH domain fusions contain amino acids 179 to 311 (TAPP2) or 169 to 329 (TAPP1). N-terminal PH domain fusions contain amino acids 3 to 156 (TAPP2) or 4 to 158 (TAPP1). Point mutations in the TAPP1 or TAPP2 C-terminal PH domains were created by primer-directed mutagenesis. All vector inserts were created by using high-fidelity PCR with restriction-tagged primers, and the final constructs were verified by restriction digestion and DNA sequencing. Constructs encoding the Btk or PLC
PH domain fused to EGFP were gifts from T. Balla (National Institutes of Health [NIH], Bethesda, Md.). Vectors encoding the PI3K p110-CD2 or PI3K p110-CD2 R916P fusion protein (43) were a gift from D. Cantrell (London, United Kingdom). Expression of this construct was confirmed by surface staining with phycoerythrin-conjugated anti-rat CD2 (BD Pharmingen) and analysis on a FACScalibur instrument (Becton Dickinson).
Transient transfection of BJAB cells with EGFP fusion constructs and live-cell imaging. BJAB cells (an atypical IgM-positive, Epstein-Barr virus [EBV]-negative Burkitt's lymphoma) were cultured in RPMI 1640 medium containing 10% fetal calf serum (FCS) and antibiotics. For transient transfection experiments, BJAB cells were washed and resuspended in a high-resistance buffer (27 mM sodium phosphate [pH 7.5]-150 mM sucrose) at 2.5 x 107/ml. A 400-µl volume of cells was mixed with 10 µg of the indicated plasmid constructs in a 0.4-cm gap electroporation cuvette (Bio-Rad, Hercules, Calif.) and incubated on ice for 10 min. Cells were electroporated by using a GenePulser II apparatus equipped with an RF module (Bio-Rad) set at 340 V, a 4-ms burst, 100% modulation, 40 kHz, five bursts, and a 1-ms burst interval. Cuvettes were incubated on ice for a further 10 min; then the contents were transferred to a tube containing 10 ml of complete RPMI medium containing 1% FCS and were plated in 8-well LabTek chambered coverglass slides (Nunc). Chamber slides were incubated overnight in a 37°C, 5% CO2 incubator and then directly examined with an inverted laser-scanning confocal microscope (Olympus Fluoview). The EGFP fluorescence signal was detected with 488-nm excitation and a 510-nm emission filter.
For each well, an EGFP-expressing cell was centered within the field and the focal plane was set near the center of the cell. Stimuli were then added to the well, and images were acquired at 30-s intervals. Goat anti-human IgM F(ab')2 fragments (Jackson ImmunoResearch) were used at a final concentration of 10 µg/ml. In some experiments, the PI3K inhibitor wortmannin (20 ng/ml; Sigma, St. Louis, Mo.) or LY294002 (25 µM; Biomol, Plymouth Meeting, Pa.) was added to the wells and the slides were incubated for 30 min at 37°C prior to stimulation.
Colocalization of EGFP fusions with F-actin. For F-actin localization experiments, the indicated transfectants were fixed with 3.7% paraformaldehyde and stained with rhodamine-phalloidin (Molecular Probes, Eugene, Oreg.), according to the manufacturer's protocol. Green (EGFP) and red (rhodamine) fluorescence images were acquired simultaneously by using dual 488- and 568-nm excitation and parallel photomultiplier tube detectors equipped with appropriate dichroic and emission filters. Bleedthrough between the red and green channels was minimal, as determined by single-color control samples and single excitation images of dual-color samples (data not shown). Digital overlay images were created by using ImageProPlus software (Media Cybernetics).
Quantitative kinetic analysis of plasma membrane recruitment and [Ca2+] mobilization. The ratio of membrane to cytoplasmic EGFP fluorescence intensity was determined from digital images by using ImageQuant software (Molecular Dynamics), as previously described (31). For [Ca2+] measurements, ratiometric imaging using Fluo-4 and Fura-Red dyes was employed (14, 30). Briefly, BJAB cells were resuspended in serum-free medium and loaded with Fluo-4-AM and Fura-Red-AM (Molecular Probes). Cells were then plated onto LabTek Chambered Coverglass slides (Nalge Nunc, Naperville, Ill.), stimulated with anti-IgM F(ab')2, and imaged at 10-s intervals using an excitation wavelength of 488 nm and simultaneous acquisition of green (510-nm longpass filter) and far-red (700- to 775-nm bandpass) channels. The relative [Ca2+] was then determined by dividing the green (Fluo-4) fluorescence by the far-red (Fura-Red) fluorescence for a microscopic field containing 20 to 30 cells. For each run, the data were normalized to those for frame 1 (no stimulus), and normalized data from multiple runs were averaged.
Measurement of PI(3,4)P2, PI(4,5)P2, and PI(3,4,5)P3 levels. BJAB cells were washed three times with phosphate-free medium before being resuspended at 107/ml in 99% phosphate-free medium, in which the cells were starved for 1 h. Cells were then labeled with 0.5 mCi of orthophosphate (ICN, Costa Mesa, Calif.) per ml for 1.5 h at 37oC and stimulated with 10 µg of anti-human IgM F(ab')2 fragment/ml for the indicated times. Extraction of inositol phospholipids and high-pressure liquid chromatography (HPLC) analysis of deacylated lipids were performed as described previously (46). The elution times of standard ATP, PI(1,4,5)P3, and PI(1,3,4,5)P3 (Perkin-Elmer, Boston, Mass.) are 85, 95, and 112 min, while the elution times of PI(3,4)P2, PI(4,5)P2, and PI(3,4,5)P3 are 76, 79, and 97 min, respectively. The amounts of radioactivity contained in the elution peak for each lipid (three to six fractions) were summed to give the total counts for each lipid. For each lipid, the fold increase was calculated by dividing the total counts from each stimulated sample by the total counts for the unstimulated control.
|
RESULTS |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
-helix but lacks the 3-phosphoinositide-binding motif (24). Comparison of murine TAPP2 to the EST database revealed the human counterpart of TAPP2 and clones encoding human and murine TAPP1. Alignment of the TAPP2 and TAPP1 sequences (Fig. 1B) shows that these proteins are approximately 60% identical over the region containing the N-terminal and C-terminal PH domains but share little identity in the C-terminal 100 amino acids. Strikingly, the N-terminal 34 amino acids are nearly identical, suggesting a strong conservation of function in this region.
Expression of TAPP1 and TAPP2 mRNAs. Expression of TAPP2 and TAPP1 transcripts in human tissues was determined by Northern blot analysis. The TAPP2 probe detected a single 5.5-kb transcript, which is predominantly expressed in lymphoid tissues such as peripheral blood leukocytes, spleen, and lymph node, but at much lower levels in the thymus (Fig. 2A). TAPP2 is also expressed at high levels in the spinal cord and thyroid gland, and at lower levels in several other tissues. The TAPP1 probe detects a single 4.5-kb transcript, except in the testis, where an abundant 2.5-kb transcript is detected. TAPP1 is expressed at the highest levels in the testis, spinal cord, and thyroid gland but is also expressed in all lymphoid tissues, though only very weakly in the thymus.
|
TAPP2 and TAPP1 are recruited to the plasma membrane after BCR ligation. Given that the PH domains of TAPP1 and TAPP2 are closely related to that of Bam32 and contain the 3-phosphoinositide-binding motif, we hypothesized that these domains function to target these molecules to the plasma membrane upon activation of PI3K. To test this possibility, we generated plasmid constructs encoding TAPP1 or TAPP2 fused to the fluorescent marker protein EGFP. These fusion proteins were expressed in human B-lymphoma cells, and the cells were activated by antibody cross-linking of the endogenous BCR, which is known to activate PI3K (17, 18). The subcellular localizations of the fluorescent proteins were assessed by live-cell imaging with a confocal microscope (Fig. 3). Before stimulation, these proteins generally showed a diffuse cytoplasmic and nuclear distribution, similar to EGFP alone. After stimulation, the Bam32, TAPP1, and TAPP2 fusion proteins showed a clear redistribution of the plasma membrane within 5 min, while EGFP alone showed no change in distribution. This result demonstrates that the TAPPs can be recruited to the plasma membranes of B lymphocytes by stimulation through a receptor known to activate PI3K.
|
|
TAPP1 and TAPP2 colocalize with F-actin within membrane ruffles. A striking feature of TAPP1 and TAPP2 membrane recruitment induced by either anti-IgM treatment or transmembrane PI3K expression was the strong association of these molecules with rapidly moving plasma membrane structures that appear to represent membrane ruffles or filopodia. To examine whether these structures represent areas of cytoskeletal reorganization and actin polymerization, we examined the relative distributions of filamentous actin and TAPP1 or TAPP2 in cells overexpressing active PI3K (Fig. 5). Clear colocalization of EGFP-TAPP1 or EGFP-TAPP2 and filamentous actin could be observed within these structures. EGFP-Bam32 showed a similar pattern, while EGFP alone showed no preferential colocalization with F-actin. The N-terminal PH domain of TAPP1 or TAPP2 also failed to show colocalization with F-actin (data not shown). This result indicates that this group of PH domain adaptors preferentially associates with membrane ruffles in activated B lymphocytes, as has been reported for other PH domains in other cell types (33, 51, 59).
|
|
|
(Fig. 7A). Membrane recruitment of the Btk PH domain, which binds to PIP3 (38, 44), was generally weak and occurred rapidly (within 1 min) and transiently, with visible membrane association disappearing by 5 min after stimulation. The PLC PH domain, which binds to the constitutively present phosphoinositide PI(4,5)P2 (16, 28), shows constitutive association with the plasma membranes of the B-lymphoma cells (Fig. 7). A transient redistribution of protein to the cytoplasm is clearly visible within 30 s of stimulation, as has been observed for other cell types (47, 54, 55). This redistribution is thought to reflect both the transient depletion of membrane PI(4,5)P2 due to the activation of PLC and PI3K enzymes and the production of the soluble IP3, which can also bind to the PLC PH domain (22, 54). Thus, PI3K and PLC activation appears to occur very rapidly in our BJAB live-cell imaging system.
Membrane recruitment of Bam32 and TAPP2 coincides with peak PI(3,4)P2 generation rather than peak PI(3,4,5)P3 or calcium mobilization responses.
In order to obtain a better measure of the relative kinetics and magnitude of PH domain-mediated redistribution events, we analyzed the fluorescence image data to obtain an averaged quantitative representation of the change in the ratio of membrane to cytoplasmic fluorescence over time (Fig. 8A). We also measured the change in intracellular free [Ca2+] over time in order to compare the kinetics of this response to the PH domain-mediated redistribution events (Fig. 8C). It was found that the Ca2+ mobilization response is initiated with rapid kinetics (within 30 s) that parallel the redistribution of the PLC and Btk PH domains. In contrast, membrane recruitment of TAPP2 is relatively delayed, becoming apparent at 2 to 3 min after stimulation. Remarkably, membrane localization of Bam32 and TAPP2 was still strong after 30 and 60 min of stimulation, while no membrane localization of Btk was detectable (Fig. 8B). Similar results were obtained for TAPP1 (data not shown).
|
PH domain. Together, the quantitative kinetics analyses indicate that membrane recruitment of the TAPPs occurs well after an initial series of signal transduction events involving PI3K, including PI(3,4,5)P3 production, Btk membrane recruitment, PI(4,5)P2 depletion, and Ca2+ mobilization. This suggests that these proteins are unlikely to play a critical role in Ca2+ responses but are recruited later, presumably in response to peak PI(3,4)P2 levels, perhaps functioning to link the BCR to mitogen-activated protein kinase (MAPK) activation or cytoskeletal rearrangement.
|
DISCUSSION |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
Phospholipid-binding ability appears to be a function shared by the majority of PH domains; however, only a subset of PH domains possess the ability to bind with high affinity to the D3 phosphoinositides generated by PI3K (24, 27). The C-terminal, but not the N-terminal, PH domains of TAPP1 and TAPP2 contain the sequence motif that is associated with D3 binding. Consistent with the hypothesis that the C-terminal PH domains mediate binding to D3 phosphoinositides, we find that these domains can target EGFP to the plasma membrane in a PI3K-dependent fashion. Furthermore, we show that active PI3K is sufficient for membrane recruitment through the C-terminal PH domain, showing that recruitment does not require activation of additional pathways and may be a direct outcome of PI3K activity. Consistent with the latter idea, mutations in the phosphoinositide-binding pocket of the TAPPs abolish membrane recruitment.
A recent study defining the in vitro lipid-binding properties of recombinant TAPP1 and TAPP2 PH domains concluded that both of these proteins bind specifically to the PI3K product PI(3,4)P2 (12). Consistent with our in vivo membrane recruitment studies, the N-terminal PH domains of TAPP1 and TAPP2 did not show significant phosphoinositide-binding activity in vitro. Thus, our findings on BCR-activated membrane recruitment of the TAPPs are consistent with a model where BCR ligation leads to PI3K activation and production of PI(3,4)P2, which drives the initial membrane recruitment response. PH domains have also been shown to be involved in protein-protein interactions, such as binding to the ß subunits of heterotrimeric G proteins (53), PKC isoforms (60), or F-actin (59). Since active PI3K is both necessary and sufficient for membrane recruitment of Bam32 and the TAPPs, it appears that protein ligands may not play an essential role in membrane recruitment of these molecules. Alternatively, putative protein ligands may be constitutively present and accessible in the plasma membrane or may themselves be targets of PI3K.
Expression of active PI3K in COS cells has been shown to induce actin reorganization and membrane ruffling through activation of Rac (43). Recent studies indicate that some PH domain proteins are selectively recruited to sites of cytoskeletal activity such as ruffles, filopodia, and lamellipodia (33, 35, 51), suggesting that PI3K effectors recruited through PH domains may play a role in cytoskeletal reorganization. We find that TAPP1, TAPP2, and Bam32 strongly colocalize with F-actin in PI3K-induced membrane ruffles in B cells. One possible explanation for this finding is that cytoskeletal elements may play a role in membrane recruitment of the TAPPs by stabilizing the PH domain-lipid interaction and promoting stable docking in membrane-associated complexes. However, actin reorganization does not appear to be essential for membrane recruitment, since inhibition of F-actin turnover using cytochalasin D fails to inhibit recruitment (data not shown). Alternatively, PI(3,4)P2 may selectively accumulate in cytoskeletally active, ruffled areas of the plasma membrane. We hypothesize that the TAPPs may be functionally linked to cytoskeletal rearrangement downstream of the initial phosphoinositide-driven membrane recruitment.
To our knowledge, this is the first study reporting the visualization and quantitation of PI3K-dependent membrane recruitment of PH domain proteins in live human B cells. The ability to clearly visualize membrane recruitment of Bam32 and the TAPPs in response to BCR stimulation is likely due to the inherent properties of their PH domains, since recruitment of these proteins is considerably stronger than that of other PH domain proteins such as Btk (Fig. 7 and 8) and Grp1 (data not shown). Membrane recruitment of Bam32 and the TAPPs in BJAB cells follows relatively slow kinetics and is sustained for prolonged periods after activation. This, again, appears to be due to the inherent properties of this group of adaptors, since BCR-induced Btk recruitment, PLC activation, and Ca2+ mobilization occur with rapid and transient kinetics. One common property of Bam32, TAPP1, and TAPP2 which may explain these observations is their ability to bind to PI(3,4,)P2 (12, 13). In agreement with previous work on other B-cell lines (17), we find that PI(3,4)P2 is produced later and in higher quantities than PIP3 following BCR cross-linking, consistent with the observed recruitment kinetics of PIP3-binding (Btk) versus PI(3,4)P2-binding (TAPP) proteins. One important factor regulating the conversion of PIP3 to PI(3,4)P2 is the inositol phosphatase SHIP (7, 11, 23), which may favor membrane recruitment of the TAPPs over that of PIP3-specific PI3K targets such as Btk (6). Interestingly, we have recently generated evidence that PI(3,4)P2 has a function in regulating Akt activation in mast cells (46), supporting the idea that this lipid is not simply a by-product of PI(3,4,5)P3 breakdown but rather has specific signaling functions, which may be mediated in part through specific interactions with PH domain proteins such as the TAPPs. Thus, while rapid PI3K-driven recruitment of Btk plays a critical role in PLC activation, IP3 generation, and Ca2+ mobilization (8, 25, 32, 45, 50), the TAPPs likely have a distinct set of functions during the response, such as activation of Akt or MAPKs, receptor desensitization, receptor internalization, or linkage of the activated membrane to cytoskeletal rearrangement.
The distinct membrane-targeting characteristics of the PH domains examined in our study demonstrate the underlying complexity in PH domain-membrane interactions. The tagged TAPP1 and TAPP2 PH domain proteins described here provide new tools for dissecting the complex temporal and spatial regulation and function of 3-phosphoinositides during cellular activation. Given the large number of PH domain proteins in the human genome (26), the cell biology of PH domain-membrane interactions will no doubt have great functional importance in many areas of biology.
|
ACKNOWLEDGMENTS |
|---|
This work was supported by grants from the Canadian Institutes of Health Research (to A.J.M. and V.D.), Manitoba Health Research Council (to A.J.M.), and NIH (AI44257). A.J.M. is a CIHR New Investigator. V.D. is a CIHR/BCLA Scientist and a Michael Smith Foundation for Health Research Senior Scholar.
|
FOOTNOTES |
|---|
|
REFERENCES |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
2. Aman, M. J., T. D. Lamkin, H. Okada, T. Kurosaki, and K. S. Ravichandran. 1998. The inositol phosphatase SHIP inhibits Akt/PKB activation in B cells. J. Biol. Chem. 273:33922-33928.
3. Anderson, K. E., P. Lipp, M. Bootman, S. H. Ridley, J. Coadwell, L. Ronnstrand, J. Lennartsson, A. B. Holmes, G. F. Painter, J. Thuring, Z. Lim, H. Erdjument-Bromage, A. Grewal, P. Tempst, L. R. Stephens, and P. T. Hawkins. 2000. DAPP1 undergoes a PI 3-kinase-dependent cycle of plasma-membrane recruitment and endocytosis upon cell stimulation. Curr. Biol. 10:1403-1412.[CrossRef][Medline]
4. Astoul, E., S. Watton, and D. Cantrell. 1999. The dynamics of protein kinase B regulation during B cell antigen receptor engagement. J. Cell Biol. 145:1511-1520.
5. Beitz, L. O., D. A. Fruman, T. Kurosaki, L. C. Cantley, and A. M. Scharenberg. 1999. SYK is upstream of phosphoinositide 3-kinase in B cell receptor signaling. J. Biol. Chem. 274:32662-32666.
6. Bolland, S., R. N. Pearse, T. Kurosaki, and J. V. Ravetch. 1998. SHIP modulates immune receptor responses by regulating membrane association of Btk. Immunity 8:509-516.[CrossRef][Medline]
7. Brauweiler, A. M., I. Tamir, and J. C. Cambier. 2000. Bilevel control of B-cell activation by the inositol 5-phosphatase SHIP. Immunol. Rev. 176:69-74.[CrossRef][Medline]
8. Buhl, A. M., C. M. Pleiman, R. C. Rickert, and J. C. Cambier. 1997. Qualitative regulation of B cell antigen receptor signaling by CD19: selective requirement for PI 3-kinase activation, inositol-1,4,5-trisphosphate production and Ca2+ mobilization. J. Exp. Med. 186:1897-1910.
9. Choquet, D., M. Partiseti, S. Amigorena, C. Bonnerot, W. H. Fridman, and H. Korn. 1993. Cross-linking of IgG receptors inhibits membrane immunoglobulin-stimulated calcium influx in B lymphocytes. J. Cell Biol. 121:355-363.
10. Craxton, A., A. Jiang, T. Kurosaki, and E. A. Clark. 1999. Syk and Bruton's tyrosine kinase are required for B cell antigen receptor-mediated activation of the kinase Akt. J. Biol. Chem. 274:30644-30650.
11. Damen, J. E., L. Liu, P. Rosten, R. K. Humphries, A. B. Jefferson, P. W. Majerus, and G. Krystal. 1996. The 145-kDa protein induced to associate with Shc by multiple cytokines is an inositol tetraphosphate and phosphatidylinositol 3,4,5-triphosphate 5-phosphatase. Proc. Natl. Acad. Sci. USA 93:1689-1693.
12. Dowler, S., R. A. Currie, D. G. Campbell, M. Deak, G. Kular, C. P. Downes, and D. R. Alessi. 2000. Identification of pleckstrin-homology-domain-containing proteins with novel phosphoinositide-binding specificities. Biochem. J. 351:19-31.[CrossRef][Medline]
13. Dowler, S., R. A. Currie, C. P. Downs, and D. R. Alessi. 1999. DAPP1: a dual adaptor for phosphotyrosine and 3-phosphoinositides. Biochem. J. 342:7-12.
14. Floto, R. A., M. P. Mahaut-Smith, B. Somasundaram, and J. M. Allen. 1995. IgG-induced Ca2+ oscillations in differentiated U937 cells; a study using laser scanning confocal microscopy and co-loaded fluo-3 and fura-red fluorescent probes. Cell Calcium 18:377-389.[CrossRef][Medline]
15. Fruman, D. A., S. B. Snapper, C. M. Yballe, L. Davidson, J. Y. Yu, F. W. Alt, and L. C. Cantley. 1999. Impaired B cell development and proliferation in the absence of phosphoinositide 3-kinase p85. Science 283:393-397.
16. Garcia, P., R. Gupta, S. Shah, A. J. Morris, S. A. Rudge, S. Scarlata, V. Petrova, S. McLaughlin, and M. J. Rebecchi. 1995. The pleckstrin homology domain of phospholipase C-1 binds with high affinity to phosphatidylinositol 4,5-bisphosphate in bilayer membranes. Biochemistry 34:16228-16234.[CrossRef][Medline]
17. Gold, M., and R. Aebersold. 1994. Both phosphatidylinositol 3-kinase and phosphatidylinositol 4-kinase products are increased by antigen receptor signaling in B cells. J. Immunol. 152:42-50.[Abstract]
18. Gold, M., V. Chan, C. W. Turck, and A. DeFranco. 1992. Membrane Ig cross-linking regulates phosphatidylinositol 3-kinase in B lymphocytes. J. Immunol. 148:2012-2022.[Abstract]
19. Gold, M. R. 2000. Intermediary signaling effectors coupling the B-cell receptor to the nucleus. Curr. Top. Microbiol. Immunol. 245:77-134.[Medline]
20. Gold, M. R., M. P. Scheid, L. Santos, M. Dang-Lawson, R. A. Roth, L. Matsuuchi, V. Duronio, and D. L. Krebs. 1999. The B cell antigen receptor activates the Akt (protein kinase B)/glycogen synthase kinase-3 signaling pathway via phosphatidylinositol 3-kinase. J. Immunol. 163:1894-1905.
21. Helgason, C. D., C. P. Kalberer, J. E. Damen, S. M. Chappel, N. Pineault, G. Krystal, and R. K. Humphries. 2000. A dual role for Src homology 2 domain-containing inositol-5-phosphatase (SHIP) in immunity: aberrant development and enhanced function of B lymphocytes in SHIP-/- mice. J. Exp. Med. 191:781-794.
22. Hirose, K., S. Kadowaki, M. Tanabe, H. Takeshima, and M. Iino. 1999. Spatiotemporal dynamics of inositol 1,4,5-trisphosphate that underlies complex Ca2+ mobilization patterns. Science 284:1527-1530.
23. Huber, M., C. D. Helgason, M. P. Scheid, V. Duronio, R. K. Humphries, and G. Krystal. 1998. Targeted disruption of SHIP leads to Steel factor-induced degranulation of mast cells. EMBO J. 17:7311-7319.[CrossRef][Medline]
24. Isakoff, S. J., T. Cardozo, J. Andreev, Z. Li, K. M. Ferguson, R. Abagyan, M. A. Lemmon, A. Aronheim, and E. Y. Skolnik. 1998. Identification and analysis of PH domain-containing targets of phosphatidylinositol 3-kinase using a novel in vivo assay in yeast. EMBO J. 17:5374-5387.[CrossRef][Medline]
25. Kurosaki, T. 1999. Genetic analysis of B cell antigen receptor signaling. Annu. Rev. Immunol. 17:555-592.[CrossRef][Medline]
26. Lander, E. S., L. M. Linton, B. Birren, C. Nusbaum, M. C. Zody, J. Baldwin, K. Devon, K. Dewar, M. Doyle, W. FitzHugh, R. Funke, D. Gage, K. Harris, A. Heaford, J. Howland, L. Kann, J. Lehoczky, R. LeVine, P. McEwan, K. McKernan, J. Meldrim, J. P. Mesirov, C. Miranda, W. Morris, J. Naylor, C. Raymond, M. Rosetti, R. Santos, A. Sheridan, C. Sougnez, N. Stange-Thomann, N. Stojanovic, A. Subramanian, D. Wyman, J. Rogers, J. Sulston, R. Ainscough, S. Beck, D. Bentley, J. Burton, C. Clee, N. Carter, A. Coulson, R. Deadman, P. Deloukas, A. Dunham, I. Dunham, R. Durbin, L. French, D. Grafham, S. Gregory, T. Hubbard, S. Humphray, A. Hunt, M. Jones, C. Lloyd, A. McMurray, L. Matthews, S. Mercer, S. Milne, J. C. Mullikin, A. Mungall, R. Plumb, M. Ross, R. Shownkeen, S. Sims, R. H. Waterston, R. K. Wilson, L. W. Hillier, J. D. McPherson, M. A. Marra, E. R. Mardis, L. A. Fulton, A. T. Chinwalla, K. H. Pepin, W. R. Gish, S. L. Chissoe, M. C. Wendl, K. D. Delehaunty, T. L. Miner, A. Delehaunty, J. B. Kramer, L. L. Cook, R. S. Fulton, D. L. Johnson, P. J. Minx, S. W. Clifton, T. Hawkins, E. Branscomb, P. Predki, P. Richardson, S. Wenning, T. Slezak, N. Doggett, J. F. Cheng, A. Olsen, S. Lucas, C. Elkin, E. Uberbacher, M. Frazier, et al. 2001. Initial sequencing and analysis of the human genome. Nature 409:860-921.[CrossRef][Medline]
27. Lemmon, M. A., and K. M. Ferguson. 2000. Signal-dependent membrane targeting by pleckstrin homology (PH) domains. Biochem. J. 350:1-18.
28. Lemmon, M. A., K. M. Ferguson, R. O'Brien, P. B. Sigler, and J. Schlessinger. 1995. Specific and high-affinity binding of inositol phosphates to an isolated pleckstrin homology domain. Proc. Natl. Acad. Sci. USA 92:10472-10476.
29. Lioubin, M. N., P. A. Algate, S. Tsai, K. Carlberg, A. Aebersold, and L. R. Rohrschneider. 1996. p150Ship, a signal transduction molecule with inositol polyphosphate-5-phosphatase activity. Genes Dev. 10:1084-1095.
30. Lipp, P., and E. Niggli. 1993. Ratiometric confocal Ca2+ measurements with visible wavelength indicators in isolated cardiac myocytes. Cell Calcium 14:359-372.[CrossRef][Medline]
31. Marshall, A. J., H. Niiro, C. G. Lerner, T. Y. Yun, S. Thomas, C. M. Disteche, and E. A. Clark. 2000. A novel B lymphocyte-associated adaptor protein, Bam32, regulates antigen receptor signaling downstream of phosphatidylinositol 3-kinase. J. Exp. Med. 191:1319-1332.
32. Marshall, A. J., H. Niiro, T. J. Yun, and E. A. Clark. 2000. Regulation of B cell activation and differentiation by the phosphatidylinositol 3-kinase and phospholipase C pathways. Immunol. Rev. 176:30-46.[CrossRef][Medline]
33. Mukhopadhyay, S., A. S. Ramars, and D. Dash. 2001. Bruton's tyrosine kinase associates with the actin-based cytoskeleton in activated platelets. J. Cell. Biochem. 81:659-665.[CrossRef][Medline]
34. Nagel, W., P. Schilcher, L. Zeitlmann, and W. Kolanus. 1998. The PH domain and polybasic domain of cytohesin-1 cooperate specifically in plasma membrane association and cellular function. Mol. Biol. Cell 9:1981-1994.
35. Nore, B. F., L. Vargas, A. J. Mohamed, L. J. Branden, C. M. Backesjo, T. C. Islam, P. T. Mattsson, K. Hultenby, B. Christensson, and C. I. Smith. 2000. Redistribution of Bruton's tyrosine kinase by activation of phosphatidylinositol 3-kinase and Rho-family GTPases. Eur. J. Immunol. 30:145-154.[CrossRef][Medline]
36. Ono, M., H. Okada, S. Bolland, S. Yanagi, T. Kurosaki, and J. V. Ravetch. 1997. Deletion of SHIP or SHP-1 reveals two distinct pathways for inhibitory signaling. Cell 90:293-301.[CrossRef][Medline]
37. Phillips, N. E., and D. C. Parker. 1983. Fc-dependent inhibition of mouse B cell activation by whole anti-mu antibodies. J. Immunol. 130:602-606.[Abstract]
38. Rameh, L. E., A. K. Arvidsson, K. L. Carraway III, A. D. Couvillon, G. Rathbun, A. Crompton, B. VanRenterghem, M. P. Czech, K. S. Ravichandran, S. J. Burakoff, D. S. Wang, C. S. Chen, and L. C. Cantley. 1997. A comparative analysis of the phosphoinositide binding specificity of pleckstrin homology domains. J. Biol. Chem. 272:22059-22066.
39. Rameh, L. E., and L. C. Cantley. 1999. The role of phosphoinositide 3-kinase lipid products in cell function. J. Biol. Chem. 274:8347-8350.
40. Rao, V. R., M. N. Corradetti, J. Chen, J. Peng, J. Yuan, G. D. Prestwich, and J. S. Brugge. 1999. Expression cloning of protein targets for 3-phosphorylated phosphoinositides. J. Biol. Chem. 274:37893-37900.
41. Rawlings, D. J. 1999. Bruton's tyrosine kinase controls a sustained calcium signal essential for B lineage development and function. Clin. Immunol. 91:243-253.[CrossRef][Medline]
42. Rawlings, D. J., A. M. Scharenberg, H. Park, M. I. Wahl, S. Lin, R. M. Kato, A. C. Fluckiger, O. N. Witte, and J. P. Kinet. 1996. Activation of BTK by a phosphorylation mechanism initiated by SRC family kinases. Science 271:822-825.[Abstract]
43. Reif, K., C. D. Nobes, G. Thomas, A. Hall, and D. A. Cantrell. 1996. Phosphatidylinositol 3-kinase signals activate a selective subset of Rac/Rho-dependent effector pathways. Curr. Biol. 6:1445-1455.[CrossRef][Medline]
44. Salim, K., M. J. Bottomley, E. Querfurth, M. J. Zvelebil, I. Gout, R. Scaif, R. L. Margolis, R. Gigg, C. I. E. Smith, P. C. Driscoll, M. D. Waterfield, and G. Panayotou. 1996. Distinct specificity in the recognition of phosphoinositides by the pleckstrin homology domains of dynamin and the Bruton's tyrosine kinase. EMBO J. 15:6241-6250.[Medline]
45. Scharenberg, A. M., and J. P. Kinet. 1998. PtdIns-3,4,5-P3: a regulatory nexus between tyrosine kinases and sustained calcium signals. Cell 94:5-8.[CrossRef][Medline]
46. Scheid, M. P., M. Huber, J. E. Damen, M. Hughes, V. Kang, P. Neilsen, G. D. Prestwich, G. Krystal, and V. Duronio. 2002. Phosphatidylinositol (3,4,5)P3 is essential but not sufficient for protein kinase B (PKB) activation; phosphatidylinositol (3,4)P2 is required for PKB phosphorylation at Ser-473: studies using cells from SH2-containing inositol-5-phosphatase knockout mice. J. Biol. Chem. 277:9027-9035.
47. Stauffer, T. P., S. Ahn, and T. Meyer. 1998. Receptor-induced transient reduction in plasma membrane PtdIns(4,5)P2 concentration monitored in living cells. Curr. Biol. 8:343-346.[CrossRef][Medline]
48. Suzuki, H., Y. Terauchi, M. Fujiwara, S. Aizawa, Y. Yazaki, T. Kadowaki, and S. Koyasu. 1999. Xid-like immunodeficiency in mice with disruption of the p85 subunit of phosphoinositide 3-kinase. Science 283:390-392.
49. Takai, T., M. Ono, M. Hikida, H. Ohmori, and J. V. Ravetch. 1996. Augmented humoral and anaphylactic responses in FcRII-deficient mice. Nature 379:346-349.[CrossRef][Medline]
50. Takata, M., and T. Kurosaki. 1996. A role for Bruton's tyrosine kinase in B cell antigen receptor-mediated activation of phospholipase C-2. J. Exp. Med. 184:31-40.
51. Tall, E. G., I. Spector, S. N. Pentyala, I. Bitter, and M. J. Rebecchi. 2000. Dynamics of phosphatidylinositol 4,5-bisphosphate in actin-rich structures. Curr. Biol. 10:743-746.[CrossRef][Medline]
52. Toker, A., and L. C. Cantley. 1997. Signalling through the lipid products of phosphoinositide-3-OH kinase. Nature 387:673-676.[CrossRef][Medline]
53. Touhara, K., J. Inglese, J. A. Pitcher, G. Shaw, and R. J. Lefkowitz. 1994. Binding of G protein ß -subunits to pleckstrin homology domains. J. Biol. Chem. 269:10217-10220.
54. van der Wal, J., R. Habets, P. Varnai, T. Balla, and K. Jalink. 2001. Monitoring agonist-induced phospholipase C activation in live cells by fluorescence resonance energy transfer. J. Biol. Chem. 276:15337-15344.
55. Varnai, P., and T. Balla. 1998. Visualization of phosphoinositides that bind pleckstrin homology domains: calcium- and agonist-induced dynamic changes and relationship to myo-[3H]inositol-labeled phosphoinositide pools. J. Cell Biol. 143:501-510.
56. Varnai, P., K. L. Rother, and T. Balla. 1999. Phosphatidylinositol 3-kinase-dependent membrane association of the Bruton's tyrosine kinase pleckstrin homology domain visualized in single living cells. J. Biol. Chem. 274:10983-10989.
57. Venkataraman, C., G. Shankar, G. Sen, and S. Bondada. 1999. Bacterial lipopolysaccharide induced B cell activation is mediated via a phosphatidylinositol 3-kinase dependent signaling pathway. Immunol. Lett. 69:233-238.[CrossRef][Medline]
58. Venkateswarlu, K., F. Gunn-Moore, P. B. Oatey, J. M. Tavare, and P. J. Cullen. 1998. Nerve growth factor- and epidermal growth factor-stimulated translocation of the ADP-ribosylation factor-exchange factor GRP1 to the plasma membrane of PC12 cells requires activation of phosphatidylinositol 3-kinase and the GRP1 pleckstrin homology domain. J. Biochem. 335:139-146.
59. Yao, L., P. Janmey, L. G. Frigeri, W. Han, J. Fujita, Y. Kawakami, J. R. Apgar, and T. Kawakami. 1999. Pleckstrin homology domains interact with filamentous actin. J. Biol. Chem. 274:19752-19761.
60. Yao, L., Y. Kawakami, and T. Kawakami. 1994. The pleckstrin homology domain of Bruton tyrosine kinase interacts with protein kinase C. Proc. Natl. Acad. Sci. USA 91:9175-9179.
This article has been cited by other articles:
| ||||||||||||||||||||||||||||||||||||||
