Interactions between a lymphoma membrane-associated guanosine 5'-triphosphate-binding protein and the cytoskeleton during receptor patching and capping.
In this study we have used several complementary techniques to isolate and characterize a lymphoma membrane-associated 41-kDa protein that shares a number of structural and functional similarities with the alpha i subunit of the guanosine 5'-triphosphate (GTP)-binding protein (e.g., Gi alpha-like protein). In addition, using permeabilized lymphoma cells, we have found that: 1) GTP or GTP-tau-S augments, and pertussis toxin inhibits, phospholipase C (PLC) activity and receptor capping; and 2) the addition of lymphoma 41-kDa Gi alpha-like protein stimulates PLC activity and receptor patching/capping, and reverses the inhibitory effect of pertussis toxin on both activity and receptor patching/capping. Additional cytochemical and biochemical data indicate that the lymphoma 41-kDa protein is closely associated with several cytoskeletal proteins (e.g., actin, myosin, and fodrin) all of which colocalize under receptor cap structures. Furthermore, both the 41-kDa-mediated phospholipase C activity and receptor patching/capping are inhibited by cytochalasin D (a microfilament disrupting drug) and W-7 drug (a calmodulin inhibitor). Together, these data provide strong evidence for a functional association between the lymphoma membrane cytoskeleton and the 41-kDa (Gi alpha-like) protein. Specifically, this association appears to be required for the activation of phospholipase C that results in inositol triphosphate production, subsequent internal Ca2+ release, and finally surface receptor patching and capping.
Bourguignon
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LY
Department of Cell Biology and Anatomy, School of Medicine, University of Miami, FL 33101.
Walker
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G
Huang
H S
HS
D000818:Animals; D000954:Antigens, Surface / Q000378:metabolism; D002460:Cell Line; D015638:Cytochalasin D / Q000494:pharmacology; D003599:Cytoskeleton / Q000378:metabolism*; D019204:GTP-Binding Proteins / Q000378:metabolism*; D006160:Guanosine Triphosphate / Q000494:pharmacology; D007152:Immunologic Capping / Q000187:drug effects; D008223:Lymphoma / Q000378:metabolism*; D008565:Membrane Proteins / Q000378:metabolism; D051379:Mice; D008970:Molecular Weight; D010449:Peptide Mapping; D037342:Pertussis Toxin; D011940:Receptor Aggregation / Q000187:drug effects; D013449:Sulfonamides / Q000494:pharmacology; D018800:Thy-1 Antigens; D014407:Tumor Cells, Cultured; D010738:Type C Phospholipases / Q000378:metabolism; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
D000954:Antigens, Surface; D008565:Membrane Proteins; D013449:Sulfonamides; D018800:Thy-1 Antigens; D010566:Virulence Factors, Bordetella; D015638:Cytochalasin D; C017967:W 7; D006160:Guanosine Triphosphate; D037342:Pertussis Toxin; D010738:Type C Phospholipases; D019204:GTP-Binding Proteins