Plasmalemmal sealing of transected mammalian neurites is a gradual process mediated by Ca(2+)-regulated proteins.
Cultured mammalian PC12 or B104 cells do not instantaneously restore a plasmalemmal barrier (seal) after neurite transection, as measured using fluorescent dye probes of various sizes and saline solutions with different [Ca(2+)](o). Rather, transected cells gradually (from 15 to 60 min postseverance) exclude probes (dye molecules) of progressively smaller size. Furthermore, an inhibitor (calpeptin) of a Ca(2+)-activated cysteine protease (calpain) and antibodies or toxins to a Ca(2+)-regulated protein (synaptotagmin) and other membrane fusion proteins (syntaxin and synaptobrevin) inhibit plasmalemmal sealing. These data obtained using molecular probes on mammalian cell lines are consistent with previous data on invertebrate giant axons indicating that Ca(2+) plays many roles in the formation, accumulation, and fusion/interaction of vesicles gradually forming a seal at a site of plasmalemmal damage.
Department of Physiology and Biophysics, University of Texas Medical Branch, Galveston, Texas 77555-0641, USA.
Soonmoon
S
Yoo
Michael P
MP
Nguyen
Mitsunori
M
Fukuda
George D
GD
Bittner
Harvey M
HM
Fishman
D000818:Animals; D019771:Axotomy; D002118:Calcium / Q000378:metabolism*; D002135:Calcium-Binding Proteins; D002154:Calpain / Q000037:antagonists & inhibitors / Q000187:drug effects / Q000378:metabolism; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism*; D004396:Coloring Agents / Q000378:metabolism; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D004151:Dipeptides / Q000494:pharmacology; D045604:Extracellular Fluid / Q000378:metabolism; D008561:Membrane Fusion / Q000187:drug effects / Q000502:physiology*; D008562:Membrane Glycoproteins / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism; D009416:Nerve Regeneration / Q000187:drug effects / Q000502:physiology*; D009419:Nerve Tissue Proteins / Q000378:metabolism; D016501:Neurites / Q000187:drug effects / Q000378:metabolism*; D009447:Neuroblastoma; D016716:PC12 Cells; D050765:Qa-SNARE Proteins; D050683:R-SNARE Proteins; D051381:Rats; D050857:Synaptotagmins; D014407:Tumor Cells, Cultured
D002135:Calcium-Binding Proteins; D004396:Coloring Agents; D015853:Cysteine Proteinase Inhibitors; D004151:Dipeptides; D008562:Membrane Glycoproteins; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; D050765:Qa-SNARE Proteins; D050683:R-SNARE Proteins; D050857:Synaptotagmins; C071482:calpeptin; D002154:Calpain; D002118:Calcium