Alternative splicing in the C-terminus of CaV2.2 controls expression and gating of N-type calcium channels.
N-type Ca(V)2.2 calcium channels localize to presynaptic nerve terminals of nociceptors where they control neurotransmitter release. Nociceptive neurons express a unique set of ion channels and receptors important for optimizing their role in transmission of noxious stimuli. Included among these is a structurally and functionally distinct N-type calcium channel splice isoform, Ca(V)2.2e[37a], expressed in a subset of nociceptors and with limited expression in other parts of the nervous system. Ca(V)2.2[e37a] arises from the mutually exclusive replacement of e37a for e37b in the C-terminus of Ca(V)2.2 mRNA. N-type current densities in nociceptors that express a combination of Ca(V)2.2e[37a] and Ca(V)2.2e[37b] mRNAs are significantly larger compared to cells that express only Ca(V)2.2e[37b]. Here we show that e37a supports increased expression of functional N-type channels and an increase in channel open time as compared to Ca(V)2.2 channels that contain e37b. To understand how e37a affects N-type currents we compared macroscopic and single-channel ionic currents as well as gating currents in tsA201 cells expressing Ca(V)2.2e[37a] and Ca(V)2.2e[37b]. When activated, Ca(V)2.2e[37a] channels remain open for longer and are expressed at higher density than Ca(V)2.2e[37b] channels. These unique features of the Ca(V)2.2e[37a] isoform combine to augment substantially the amount of calcium that enters cells in response to action potentials. Our studies of the e37a/e37b splice site reveal a multifunctional domain in the C-terminus of Ca(V)2.2 that regulates the overall activity of N-type calcium channels in nociceptors.
Castiglioni
Andrew J
AJ
Department of Neuroscience, Box 1953, Brown University, Providence, RI 02912, USA.
Raingo
Jesica
J
Lipscombe
Diane
D
D000200:Action Potentials / Q000502:physiology; D017398:Alternative Splicing / Q000235:genetics* / Q000502:physiology; D020864:Calcium Channels, N-Type / Q000235:genetics* / Q000502:physiology; D002461:Cell Line, Transformed; D004594:Electrophysiology; D005091:Exons / Q000235:genetics; D005786:Gene Expression Regulation / Q000235:genetics* / Q000502:physiology; D006801:Humans; D015640:Ion Channel Gating / Q000235:genetics* / Q000502:physiology; D010146:Pain / Q000503:physiopathology; D012333:RNA, Messenger / Q000235:genetics; D014162:Transfection
C500545:CACNA1B protein, human; D020864:Calcium Channels, N-Type; D012333:RNA, Messenger