title: Calcium influx is required for endocytotic membrane retrieval.
abstract: Cells use endocytotic membrane retrieval to compensate for excess surface membrane after exocytosis. Retrieval is thought to be calcium-dependent, but the source of this calcium is not known. We found that, in sea urchin eggs, endocytotic membrane retrieval required extracellular calcium. Inhibitors of P-type calcium channels-cadmium, omega-conotoxin MVIIC, omega-agatoxin IVA, and omega-agatoxin TK-blocked membrane retrieval; selective inhibitors of N-type and L-type channels did not. Treatment with calcium ionophores overcame agatoxin inhibition in a calcium-dependent manner. Cadmium blocked membrane retrieval when applied during the first 5 minutes after fertilization, the period when the membrane potential is depolarized. We conclude that calcium influx through omega-agatoxin-sensitive channels plays a key role in signaling for endocytotic membrane retrieval.
authors.affiliation: Institute of Molecular Medicine and Genetics, Department of Medicine, Veterans Affairs Medical Center, Medical College of Georgia, 1120 15th Street CB 2803, Augusta, GA 30912-2630, USA. stevev@immag.mcg.edu
authors.forename: S S
authors.initials: SS
authors.lastname: Vogel
authors.forename: R M
authors.initials: RM
authors.lastname: Smith
authors.forename: B
authors.initials: B
authors.lastname: Baibakov
authors.forename: Y
authors.initials: Y
authors.lastname: Ikebuchi
authors.forename: N A
authors.initials: NA
authors.lastname: Lambert
mesh_terms: D000818:Animals; D001692:Biological Transport; D002118:Calcium / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D015220:Calcium Channels / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism*; D004705:Endocytosis; D010455:Peptides / Q000494:pharmacology; D012617:Sea Urchins; D013111:Spider Venoms / Q000494:pharmacology; D020867:omega-Agatoxin IVA; D020960:omega-Conotoxins
chemical_list: D002121:Calcium Channel Blockers; D015220:Calcium Channels; D010455:Peptides; D013111:Spider Venoms; D020867:omega-Agatoxin IVA; D020960:omega-Conotoxins; C075851:omega-conotoxin-MVIIC; D002118:Calcium