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High level expression of transfected G protein α i3 subunit is required for plasma membrane targeting and adenylyl cyclase inhibition in NIH 3T3 fibroblasts
Author(s) -
Hermouet Sylvie,
de Mazancourt Philippe,
Spiegel Allen M.,
Farquhar Marilyn Gist,
Wilson Bridget S.
Publication year - 1992
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(92)80940-i
Subject(s) - adenylyl cyclase , transfection , forskolin , gs alpha subunit , adcy10 , golgi apparatus , microbiology and biotechnology , pertussis toxin , g alpha subunit , g protein , cholera toxin , 3t3 cells , protein subunit , biology , cell culture , chemistry , biochemistry , gene , endoplasmic reticulum , signal transduction , endocrinology , genetics
The α subunits of pertussis toxin‐sensitive G proteins G i1 , G i2 and G i3 have been shown to inhibit adenylyl cyclase in transfected cells. However, G i3 has recently been associated with protein transport and localized to the Golgi apparatus in a number of cell lines, rather than to the plasma membrane. We studied NIH 3T3 clones stably expressing different levels of a constitutively activated mutant of the α subunit of G i3 (α i3 ‐Q204L). Transfected α i3 subunits were localized to the Golgi apparatus in all NIH 3T3 clones. In clones expressing α i3 ‐Q204L at high levels, α i3 subunits were also localized to the plasma membrane. Those clones which demonstrated expression of α i3 at the plasma membrane showed a 40% to 60% inhibition of forskolin‐induced cAMP accumulation. Transfected NIH 3T3 clones in which plasma membrane α i3 was undetectable, did not show inhibition of forskolin‐induced cAMP accumulation. These data suggest that, unless high expression is achieved in transfected cells, α i3 is targeted predominantly to the Golgi, not to the plasma membrane, and does not control adenylyl cyclase activity in NIH 3T3 fibroblasts.