The nature of membrane anchorage determines kinase association and detergent solubility of CD4.
The presence of a glycosylphosphatidylinositol (GPI) anchor on a membrane protein is thought to influence aspects of the protein's biochemistry. While it has been demonstrated that a GPI-anchor is sufficient for altering the detergent solubility of integral membrane proteins, it has not been shown that the anchor is sufficient for changing the phosphoprotein associations of membrane proteins. In order to define the influence of GPI-anchors on the biochemistry of membrane proteins we compared the phosphoprotein associations and detergent solubility of wild-type and GPI-anchored CD4 expressed on HSB cell transfectants. While wild-type CD4 was mostly associated with lck kinase, GPI-anchored CD4 was associated with the 'GPI-anchored pattern of phosphoproteins'. The Triton X-100 solubilities of the two forms of CD4 were also distinct: wild-type CD4 was > 95% soluble, whereas GPI-anchored CD4 was only 65% soluble. These results underscore the deterministic role of the GPI-anchor in the properties associated with GPI-anchored proteins.
Solomon
K R
KR
Infectious Disease Unit, Dana-Farber Cancer Institute, Boston, Massachusetts 02115, USA.
Mallory
M A
MA
Hanify
K A
KA
Finberg
R W
RW
D015704:CD4 Antigens / Q000737:chemistry* / Q000145:classification; D003902:Detergents / Q000494:pharmacology; D004591:Electrophoresis, Polyacrylamide Gel; D005786:Gene Expression Regulation / Q000235:genetics; D005960:Glucosides / Q000494:pharmacology; D017261:Glycosylphosphatidylinositols / Q000737:chemistry*; D006801:Humans; D007460:Iodoacetamide / Q000378:metabolism; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck) / Q000032:analysis; D008565:Membrane Proteins / Q000737:chemistry / Q000378:metabolism; D017830:Octoxynol / Q000494:pharmacology; D010750:Phosphoproteins / Q000032:analysis / Q000378:metabolism; D011233:Precipitin Tests; D011494:Protein Kinases / Q000032:analysis; D012995:Solubility; D014162:Transfection / Q000235:genetics; D014407:Tumor Cells, Cultured
D015704:CD4 Antigens; D003902:Detergents; D005960:Glucosides; D017261:Glycosylphosphatidylinositols; D008565:Membrane Proteins; D010750:Phosphoproteins; C018619:octyl-beta-D-glucoside; D017830:Octoxynol; D011494:Protein Kinases; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck); D007460:Iodoacetamide