title: Calmodulin is the divalent cation receptor for rapid endocytosis, but not exocytosis, in adrenal chromaffin cells.
abstract: Exocytosis and the ensuing rapid endocytosis in adrenal chromaffin cells are both Ca(2+)-dependent phenomena but differ in their divalent cation specificity, implying distinct Ca2+ receptors for the two processes. To ascertain whether calmodulin is the Ca2+ receptor for either process, we blocked its function by introducing calmodulin-binding peptides or anti-calmodulin antibodies into these cells. Exo/endocytosis was followed by measurement of cell membrane capacitance. Rapid endocytosis, but not exocytosis, was abolished by these treatments, indicating that calmodulin is the Ca2+ receptor for rapid endocytosis but is not involved in exocytosis. The principal calmodulin target is not protein phosphatase-2B, as antagonism of this enzyme did not inhibit but accelerated rapid endocytosis. Calmodulin may thus regulate both the rate and extent of rapid endocytosis by distinct pathways.
authors.affiliation: Department of Neurobiology and Physiology, Northwestern University, Evanston, Illinois 60208, USA.
authors.forename: C R
authors.initials: CR
authors.lastname: Artalejo
authors.forename: A
authors.initials: A
authors.lastname: Elhamdani
authors.forename: H C
authors.initials: HC
authors.lastname: Palfrey
mesh_terms: D000313:Adrenal Medulla / Q000166:cytology / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology / Q000494:pharmacology; D001464:Barium / Q000494:pharmacology; D019703:Calcineurin; D002118:Calcium / Q000502:physiology*; D002135:Calcium-Binding Proteins / Q000187:drug effects / Q000502:physiology*; D002147:Calmodulin / Q000037:antagonists & inhibitors / Q000276:immunology / Q000502:physiology*; D002148:Calmodulin-Binding Proteins / Q000037:antagonists & inhibitors; D002417:Cattle; D004705:Endocytosis / Q000502:physiology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005089:Exocytosis; D008345:Manganese / Q000494:pharmacology; D008564:Membrane Potentials / Q000187:drug effects; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000276:immunology; D010749:Phosphoprotein Phosphatases / Q000037:antagonists & inhibitors; D047428:Protein Kinase Inhibitors; D013324:Strontium / Q000494:pharmacology
chemical_list: D000911:Antibodies, Monoclonal; D002135:Calcium-Binding Proteins; D002147:Calmodulin; D002148:Calmodulin-Binding Proteins; D004791:Enzyme Inhibitors; D010446:Peptide Fragments; D047428:Protein Kinase Inhibitors; D001464:Barium; D008345:Manganese; D019703:Calcineurin; D010749:Phosphoprotein Phosphatases; D002118:Calcium; D013324:Strontium