Calmodulin Is the Divalent Cation Receptor for Rapid Endocytosis, but Not Exocytosis, in Adrenal Chromaffin Cells

• Published in: Neuron (Cambridge, Mass.) Mass.), 1996, Vol.16 (1), p.195-205
• Main Authors: Artalejo, Cristina R, Elhamdani, Abdeladim, Palfrey, H.Clive
• Format: Article
• Language: English
• Subjects: Adrenal Medulla - cytology; Adrenal Medulla - metabolism; Amino Acid Sequence; Animals; Antibodies, Monoclonal - immunology; Antibodies, Monoclonal - pharmacology; Barium - pharmacology; Calcineurin; Calcium - physiology; Calcium-Binding Proteins - drug effects; Calcium-Binding Proteins - physiology; Calmodulin - antagonists & inhibitors; Calmodulin - immunology; Calmodulin - physiology; Calmodulin-Binding Proteins - antagonists & inhibitors; Cattle; Endocytosis - physiology; Enzyme Inhibitors - pharmacology; Exocytosis; Manganese - pharmacology; Membrane Potentials - drug effects; Molecular Sequence Data; Peptide Fragments - immunology; Phosphoprotein Phosphatases - antagonists & inhibitors; Protein Kinase Inhibitors; Strontium - pharmacology
• ISSN: 0896-6273; 1097-4199
• DOI: 10.1016/S0896-6273(00)80036-7

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 Ca 2+ receptors for the two processes. To ascertain whether calmodulin is the Ca 2+ 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 Ca 2+ 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.