Two-dimensional distribution of Gi2alpha in the plasma membrane: a critical evaluation by immunocytochemistry.
Caveolae have been postulated as a center for signal transduction, because many signaling molecules are concentrated in caveolin-rich fractions. We took Gi2alpha as an example and examined whether it is constitutively concentrated in caveolae. First, the behavior of caveolin and Gi2alpha in density-equilibrium ultracentrifugation was reexamined. By collecting fractions efficiently, caveolin and Gi2alpha were found to distribute differently. Secondly, by novel immunocytochemical methods it was found that the labeling density of Gi2alpha was 2.29 times higher in caveolae than in the non-caveolar plasma membrane. The results indicate that the concentration of Gi2alpha in caveolae is lower than deduced from most biochemical studies.
Nomura
R
R
Department of Anatomy and Cell Biology, Gunma University School of Medicine, Maebashi, Japan.
Inuo
C
C
Takahashi
Y
Y
Asano
T
T
Fujimoto
T
T
D051242:Caveolin 1; D022461:Caveolins; D002458:Cell Fractionation; D002460:Cell Line; D002462:Cell Membrane / Q000737:chemistry* / Q000648:ultrastructure; D002499:Centrifugation, Density Gradient; D004591:Electrophoresis, Polyacrylamide Gel; D005455:Fluorescent Antibody Technique; D005614:Freeze Fracturing; D051960:GTP-Binding Protein alpha Subunit, Gi2; D019206:GTP-Binding Protein alpha Subunits, Gi-Go; D019204:GTP-Binding Proteins / Q000032:analysis*; D015151:Immunoblotting; D007150:Immunohistochemistry; D008565:Membrane Proteins / Q000032:analysis; D016253:Microscopy, Immunoelectron; D017830:Octoxynol; D011518:Proto-Oncogene Proteins / Q000032:analysis*; D015398:Signal Transduction
D051242:Caveolin 1; D022461:Caveolins; D008565:Membrane Proteins; D011518:Proto-Oncogene Proteins; D017830:Octoxynol; D019204:GTP-Binding Proteins; D051960:GTP-Binding Protein alpha Subunit, Gi2; D019206:GTP-Binding Protein alpha Subunits, Gi-Go