A substantial proportion of cardiac Gs is not associated with the plasma membrane

FEBS Letters

Leiber, Denis¹  Roth, David A.¹  Hammond, H.Kirk¹  Insel, Paul A.¹  Urasawa, Kazushi¹ 

[1] VAMC-San Diego, San Diego, CA, 92161, USA

关键词: G-protein;    Signal transduction;    Myocardium;    cyc reconstitution;    immunoblotting;    Cholera toxin;    ADP-ribosylation;    G-protein;    guanine nucleotide-binding protein;    Gs;    the G-protein that mediates stimulation of adenylyl cyclase (EC 4.6.1.1) αs;    the α subunit of Gs;    βγ;    the β and γ subunit dimer of G proteins;    K+-pNPPase;    K+-stimulated p-nitrophenyl phosphatase;   

DOI  :  10.1016/0014-5793(92)80400-B

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

The precise interactions between the subunits of G_s, (α, β, γ) and the plasma membrane remain to be established. If α_s is associated loosely with the inner membrane, is labile during activation, or is always present to some extent in the cytoplasm, then it should fractionate to the supernatant of a high-speed centrifugation. We identified abundant α, (52–66% of total cellular) in the supernatant fraction of right atrial and left ventricular membrane preparations of porcine heart as shown by two distinct measures of α, (immunoblotting and ADP ribosylation by cholera toxin). However, functional assays utilizing reconstitution of cardiac α, with cyc S49 membranes revealed that the supernatant fraction contained ∼16% of total cellular α_s activity. The α_s present in the supernatant fraction did not result from contamination by sarcolemmal membrane fragments. We conclude that traditional methods for quantifying α, which utilize only detergent extracts from high-speed pellets do not account for a sizable proportion of total cellular α_s but that the majority of this population of cardiac α_s may not be functional, at least with respect to adenylyl cyclase activation.

【 授权许可】

Unknown