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Mol. Cell. Biol., Jul 1995, 3664-3671, Vol 15, No. 7
H Ishii, T Yoshida, H Oh, S Yoshida and M Terada
The K-sam gene was originally cloned from KATO-III human gastric cancer
cells and is identical to the bek or keratinocyte growth factor (KGF)
receptor (KGFR) or fibroblast growth factor receptor 2 gene. K-sam
generates several variant transcripts by alternative splicing, and the most
abundant K-sam transcript in KATO-III cells was cloned as the K- sam-IIC3
cDNA, which has the KGF-binding motif and a short carboxyl terminus lacking
a putative phospholipase C-gamma 1 association site, Tyr-769. The
K-sam-IIC3 cDNA was distinct from the K-sam-IIC1 cDNA, which was the same
as the previously reported KGFR cDNA. The K-sam-IIC1 product contains a
long carboxyl terminus with Tyr-769. K-sam-IIC3 showed greater transforming
activity in NIH 3T3 cells than did K-sam- IIC1, and in gastric cancer cell
lines in general, the level of K-sam- IIC3 mRNA was greater than that of
K-sam-IIC1 mRNA. Here we report that the K-sam-IIC3 product was less
autophosphorylated than the K-sam-IIC1 product in NIH 3T3 transfectants.
K-sam-IIC3-transfected keratinocytes showed a stronger mitogenic response
to KGF than did K-sam-IIC1 transfectants. Moreover, K-sam-IIC3-transfected
L6 myoblast cells hardly differentiated when cultured in
differentiation-inducing medium and growth was not significantly affected,
while K-sam-IIC1 transfectants showed a differentiated phenotype with a
reduced growth rate. These data indicate the difference in the signal
transduction mediated by two KGFR-type K-sam variants generated by
alternative splicing which might be involved in certain differentiation and
carcinogenesis scenarios.
Copyright © 1995, American Society for Microbiology
A truncated K-sam product lacking the distal carboxyl-terminal portion provides a reduced level of autophosphorylation and greater resistance against induction of differentiation
Genetics Division, National Cancer Center Research Institute, Tokyo, Japan.
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