FMRFamide and membrane stretch as activators of the Aplysia S-channel.
The long-standing distinction between channels and transporters is becoming blurred, with one pump protein even able to convert reversibly to a channel in response to osmotic shock. In this light, it is plausible that stretch channels, membrane proteins whose physiological roles have been elusive, may be transporters exhibiting channel-like properties in response to mechanical stress. We recently described a case, however, where this seems an unlikely explanation. An Aplysia K channel whose physiological pedigree is well established (it is an excitability-modulating conductance mechanism) was found able to be activated by stretch. Here we establish more firmly the identity of this Aplysia conductance, the S-channel, as a stretch channel. We show that the permeation and fast kinetic properties of the stretch-activated channel and of the FMRFamide-activated S-channel are indistinguishable. We have also made progress in extending the kinetic analysis of the stretch channel to situations of multiple channel activity. This analysis implements a novel renewal theory approach and is therefore explained in some detail.
Vandorpe
D H
DH
Department of Biology, University of Ottawa, Ontario, Canada.
Small
D L
DL
Dabrowski
A R
AR
Morris
C E
CE
D000818:Animals; D001048:Aplysia; D002462:Cell Membrane / Q000502:physiology; D002478:Cells, Cultured; D019835:FMRFamide; D017952:Ganglia, Invertebrate / Q000502:physiology; D007447:Invertebrate Hormones / Q000494:pharmacology; D015640:Ion Channel Gating; D007473:Ion Channels / Q000187:drug effects / Q000502:physiology*; D007700:Kinetics; D008433:Mathematics; D008564:Membrane Potentials / Q000187:drug effects; D008954:Models, Biological; D009475:Neurons, Afferent / Q000187:drug effects / Q000502:physiology*; D009479:Neuropeptides / Q000494:pharmacology*; D011188:Potassium / Q000494:pharmacology; D026902:Potassium Channel Blockers; D013314:Stress, Mechanical; D019789:Tetraethylammonium; D013757:Tetraethylammonium Compounds / Q000494:pharmacology
D007447:Invertebrate Hormones; D007473:Ion Channels; D009479:Neuropeptides; D026902:Potassium Channel Blockers; D013757:Tetraethylammonium Compounds; D019835:FMRFamide; D019789:Tetraethylammonium; D011188:Potassium