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.
Publication types
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Adrenal Medulla / cytology
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Adrenal Medulla / metabolism*
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Amino Acid Sequence
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Animals
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Antibodies, Monoclonal / immunology
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Antibodies, Monoclonal / pharmacology
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Barium / pharmacology
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Calcineurin
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Calcium / physiology*
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Calcium-Binding Proteins / drug effects
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Calcium-Binding Proteins / physiology*
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Calmodulin / antagonists & inhibitors
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Calmodulin / immunology
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Calmodulin / physiology*
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Calmodulin-Binding Proteins / antagonists & inhibitors
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Cattle
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Endocytosis / physiology*
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Enzyme Inhibitors / pharmacology
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Exocytosis*
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Manganese / pharmacology
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Membrane Potentials / drug effects
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Molecular Sequence Data
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Peptide Fragments / immunology
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Phosphoprotein Phosphatases / antagonists & inhibitors
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Protein Kinase Inhibitors
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Strontium / pharmacology
Substances
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Antibodies, Monoclonal
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Calcium-Binding Proteins
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Calmodulin
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Calmodulin-Binding Proteins
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Enzyme Inhibitors
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Peptide Fragments
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Protein Kinase Inhibitors
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Barium
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Manganese
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Calcineurin
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Phosphoprotein Phosphatases
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Calcium
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Strontium