Clonal variation of adenylyl cyclase activity in a rat tumor cell line caused by change in G protein-catalytic unit interaction
✍ Scribed by Masahiro Kawabata; Hiroshi Yoshikura; Keizo Horio; Kenji Fujiwara; Aikichi Iwamoto
- Publisher
- John Wiley and Sons
- Year
- 1990
- Tongue
- English
- Weight
- 955 KB
- Volume
- 144
- Category
- Article
- ISSN
- 0021-9541
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✦ Synopsis
Two subclones of the rat XC cell line characteriLed by different morphology exhibitcd quite diiierent adenylyl cyrlase responses upon various stimulations.
Upon treatment with cholera toxin, clone KK1 accumulated a high level of intracellular CAMP thereby changing its polygonal morphology to an elongated morphology, while the other clone, LK1, with a fibroblastic morphology, failed to increase the intracellular CAMP and remained morphologically unchanged. When membrane fractions derived from these two clones were stimulated with 10 pM forskolin, 10 pM GTPyS, or 10 tnM NaF, fiveto 20-fold more CAMP w a s accumulated in KK1 derived membranes than in I.K1 -derived membranes. With the same membrane fractions, upon treatment with M n ' ' , which directly stiniulates the catalytic unit, a high level of CAMP was accumulated both in RK1 and LK1, indicating that thc catalytic function inducible by M n ' ' was 5imilar in both clones. There was no significant diiierence in the level of expression of G protein a>, ai (at least a,, and a l l ) , and p subunits between LK1 and KK1. Cholate extracts of the membrane proteins of LK1 and RK1 reconstituted the adenylyl cyclase dclivity of the cyc-variant of S-19 lyrriphonia cells to the same level. Therefore, it is inferred that the defect in L.K1 resides in the interaction of stimulatory G proteins and the actual catalyst.