Calcium and ionophore A23187 stimulates deposition of extracellular matrix and acetylcholinesterase release in cultured myotubes.
Calcium (Ca2+) and calcium-transporting ionophores stimulate protein secretion in many cellular systems. We demonstrate here than increases in intracellular calcium concentration induce a time- and concentration-dependent deposition of extracellular matrix and an increase in acetylcholinesterase secretion. Scanning and transmission electron-microscopy revealed that treatment with the calcium ionophore A23187, or high extracellular Ca2+ levels (5 mM to 15 mM) produce significant deposits of extracellular matrix around the myotubes, as well as a marked increase in the acetylcholinesterase reaction-product. Blocking muscle contraction was not necessary for the induction of AChE secretory activity. Sucrose density-gradients of media conditioned by muscle cells revealed 3 separate acetylcholinesterase molecular forms. However, incubation with A23187 increased only the 4.5 S and the 7.2 S molecular forms, whereas the 12.0 S form showed no significant differences from controls. Polyacrylamide gel electrophoresis, and autoradiography using [3H]diisopropyl fluorophosphate revealed a broad band at 65,000 daltons. This band was broader than for controls when medium was obtained from A23187-treated cells. Our results show that increasing intracellular Ca2+ concentration induces marked deposition of extracellular matrix and increased acetylcholinesterase secretion, with an apparent selectivity for the monomeric and dimeric acetylcholinesterase molecular forms.
Bursztajn
S
S
Department of Psychiatry, Harvard Medical School, Mailman Research Center, Belmont, MA 02178.
Schneider
L W
LW
Jong
Y J
YJ
Berman
S A
SA
D000110:Acetylcholinesterase / Q000378:metabolism*; D000818:Animals; D001345:Autoradiography; D000001:Calcimycin / Q000494:pharmacology*; D002118:Calcium / Q000494:pharmacology*; D002478:Cells, Cultured; D002642:Chick Embryo; D004591:Electrophoresis, Polyacrylamide Gel; D005109:Extracellular Matrix / Q000378:metabolism* / Q000648:ultrastructure; D008855:Microscopy, Electron, Scanning; D009132:Muscles / Q000166:cytology / Q000196:embryology / Q000378:metabolism*; D012633:Secretin / Q000378:metabolism
D012633:Secretin; D000001:Calcimycin; D000110:Acetylcholinesterase; D002118:Calcium