Calcium influx is required for endocytotic membrane retrieval.
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.
Vogel
S S
SS
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
Smith
R M
RM
Baibakov
B
B
Ikebuchi
Y
Y
Lambert
N A
NA
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
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