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Clonal variation of adenylyl cyclase activity in a rat tumor cell line caused by change in G protein‐catalytic unit interaction
Author(s) -
Kawabata Masahiro,
Yoshikura Hiroshi,
Horio Keizo,
Fujiwara Kenji,
Iwamoto Aikichi
Publication year - 1990
Publication title -
journal of cellular physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.529
H-Index - 174
eISSN - 1097-4652
pISSN - 0021-9541
DOI - 10.1002/jcp.1041440312
Subject(s) - adenylyl cyclase , cholera toxin , forskolin , gs alpha subunit , intracellular , adcy10 , g protein , cyclase , clone (java method) , biology , gtp' , chemistry , camp dependent pathway , cell culture , microbiology and biotechnology , adcy9 , biochemistry , enzyme , receptor , genetics , gene
Two subclones of the rat XC cell line characterized by different morphology exhibited quite different adenylyl cyclase responses upon various stimulations. Upon treatment with cholera toxin, clone RK1 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 μM forskolin, 10 μM GTPλS, or 10 mM NaF, five‐ to 20‐fold more cAMP was accumulated in RK1‐derived membranes than in LK1‐derived membranes. With the same membrane fractions, upon treatment with Mn ++ , which directly stimulates the catalytic unit, a high level of cAMP was accumulated both in RK1 and LK1, indicating that the catalytic function inducible by Mn ++ was similar in both clones. There was no significant difference in the level of expression of G protein α 2 , α i (at least α i1 and α i2 ), and β subunits between LK1 and RK1. Cholateextracts of the membrane protein of LK1 and RK1 reconstituted the adenylyl cyclase activity of the cyc variant of S49 lymphoma cells to the same level. Therefore, it is inferred that the defect in LK1 resides in the interaction of stimulatory G proteins and the actual catalyst.