Regulation of ANF receptor internalization: involvement of extracellular calcium.
Receptor mediated internalization of 125I-ANF (99-126) and the underlying mechanism was studied in PC12 cells. Phosphorylation of PC12 cell plasma membrane proteins at 0 degrees C or 37 degrees C was not altered in presence of ANF (99-126) or c-ANF (4-23). Exposure of cells to phorbol 12-myristate 13-acetate (PMA, 100 ng/ml) did not alter the endocytic rate or extent of 125I-ANF (99-126) internalization. When cells were treated with a combination of PMA and the calcium ionophore A23187, internalization was not stimulated. Incubation with A23187 (10 microM) alone decreased 125I-ANF (99-126) internalization by 22% in Ca2+ containing medium. Cell surface binding increased 10% in the presence of Ca2+ compared to Ca2+ free medium, irrespective of the presence of A23187. Ca2+ appears to play an important role in the binding of ANF to the receptor and initiation of ligand-receptor complex internalization. Activation of protein kinase C or receptor phosphorylation is not an essential step in initiating ANF receptor internalization.
Rathinavelu
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Department of Pharmacology and Toxicology, School of Pharmacy and Pharmacal Sciences, Purdue University, West Lafayette, IN 47907.
Isom
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D000310:Adrenal Gland Neoplasms; D000818:Animals; D009320:Atrial Natriuretic Factor / Q000378:metabolism*; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000494:pharmacology*; D002462:Cell Membrane / Q000378:metabolism; D007700:Kinetics; D008565:Membrane Proteins / Q000302:isolation & purification / Q000378:metabolism; D008970:Molecular Weight; D010673:Pheochromocytoma; D010750:Phosphoproteins / Q000302:isolation & purification; D010766:Phosphorylation; D051381:Rats; D017461:Receptors, Atrial Natriuretic Factor; D011956:Receptors, Cell Surface / Q000187:drug effects / Q000378:metabolism*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
D008565:Membrane Proteins; D010750:Phosphoproteins; D011956:Receptors, Cell Surface; D000001:Calcimycin; D009320:Atrial Natriuretic Factor; D017461:Receptors, Atrial Natriuretic Factor; D013755:Tetradecanoylphorbol Acetate; D002118:Calcium