Defect of receptor-G protein coupling in human gallbladder with cholesterol stones.
Human gallbladders with cholesterol stones (ChS) exhibit an impaired muscle contraction and relaxation and a lower CCK receptor-binding capacity compared with those with pigment stones (PS). This study was designed to determine whether there is an abnormal receptor-G protein coupling in human gallbladders with ChS using (35)S-labeled guanosine 5'-O-(3-thiotriphosphate) ([(35)S]GTPgammaS) binding, (125)I-labeled CCK-8 autoradiography, immunoblotting, and G protein quantitation. CCK and vasoactive intestinal peptide caused significant increases in [(35)S]GTPgammaS binding to Galpha(i-3) and G(s)alpha, respectively. The binding was lower in ChS than in PS (P < 0.01). The reduced [(35)S]GTPgammaS binding in ChS was normalized after the muscles were treated with cholesterol-free liposomes (P < 0.01). Autoradiography and immunoblots showed a decreased optical density (OD) for CCK receptors, an even lower OD value for receptor-G protein coupling, and a higher OD for uncoupled receptors or Galpha(i-3) protein in ChS compared with PS (P < 0.001). G protein quantitation also showed that there were no significant differences in the Galpha(i-3) and G(s)alpha content in ChS and PS. We conclude that, in addition to an impaired CCK receptor-binding capacity, there is a defect in receptor-G protein coupling in muscle cells from gallbladder with ChS. These changes may be normalized after removal of excess cholesterol from the plasma membrane.
Xiao
Z L
ZL
Departments of Medicine and Surgery, Rhode Island Hospital and Brown University School of Medicine, Providence, Rhode Island 02903, USA.
Chen
Q
Q
Amaral
J
J
Biancani
P
P
Behar
J
J
D001345:Autoradiography; D002766:Cholecystokinin / Q000494:pharmacology; D002769:Cholelithiasis / Q000737:chemistry / Q000503:physiopathology*; D002784:Cholesterol / Q000032:analysis*; D003432:Cross-Linking Reagents / Q000494:pharmacology; D019204:GTP-Binding Proteins / Q000378:metabolism*; D005704:Gallbladder / Q000503:physiopathology*; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000378:metabolism; D006801:Humans; D015151:Immunoblotting; D007163:Immunosorbent Techniques; D007457:Iodine Radioisotopes; D009119:Muscle Contraction; D009130:Muscle, Smooth / Q000503:physiopathology; D011949:Receptors, Cholecystokinin / Q000378:metabolism*; D012844:Sincalide / Q000378:metabolism; D013462:Sulfur Radioisotopes; D014660:Vasoactive Intestinal Peptide / Q000494:pharmacology
D003432:Cross-Linking Reagents; D007457:Iodine Radioisotopes; D011949:Receptors, Cholecystokinin; D013462:Sulfur Radioisotopes; D014660:Vasoactive Intestinal Peptide; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D002766:Cholecystokinin; D002784:Cholesterol; D019204:GTP-Binding Proteins; D012844:Sincalide