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Endocytosis‐Dominated Membrane Area Decrease Requires Rab5 Protein in Rat Melanotrophs
Author(s) -
SEDEJ SIMON,
RUPNIK MARJAN,
ZOREC ROBERT
Publication year - 2005
Publication title -
annals of the new york academy of sciences
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.712
H-Index - 248
eISSN - 1749-6632
pISSN - 0077-8923
DOI - 10.1196/annals.1342.024
Subject(s) - endocytosis , exocytosis , receptor mediated endocytosis , membrane , extracellular , microbiology and biotechnology , biophysics , chemistry , membrane protein , cell membrane , bulk endocytosis , biology , receptor , biochemistry
A bstract : Eukaryotic cells internalize extracellular macromolecules by endocytosis and it was shown that Rab5 protein is required for this process. While it is clear that endocytosis consists of vesicle fission from the plasma membrane, the role of Rab5 protein in the plasma membrane surface area changes is still unclear. Here we studied whether Rab5 is required for membrane surface area changes in rat melanotrophs—cells deriving from the pituitary pars intermedia . The presence of this protein in melanotrophs was probed by immunocytochemistry and its putative role in membrane area dynamics was monitored electrophysiologically with membrane capacitance measurements as this parameter directly reflects changes in membrane surface area. We found that Rab5 protein exists in melanotrophs. At [Ca 2+ ] i < 3 μM, endocytosis‐dominated membrane capacitance decrease was found to be blocked by microinjection of specific Rab5 antibody. At high [Ca 2+ ] i , Rab5 antibody did not affect the steady‐state increase in membrane capacitance, while it elevated the rate of membrane capacitance increase, which is consistent with an inhibition of endocytosis.