Genetic, cellular, and functional evidence for Ca2+ inflow through Cav1.2 and Cav1.3 channels in murine spiral ganglion neurons.
Spiral ganglion neurons (SGNs) of the eighth nerve serve as the bridge between hair cells and the cochlear nucleus. Hair cells use Cav1.3 as the primary channel for Ca(2+) inflow to mediate transmitter release. In contrast, SGNs are equipped with multiple Ca(2+) channels to mediate Ca(2+)-dependent functions. We examined directly the role of Cav1.3 channels in SGNs using Cav1.3-deficient mice (Cav1.3(-/-)). We revealed a surprising finding that SGNs functionally express the cardiac-specific Cav1.2, as well as neuronal Cav1.3 channels. We show that evoked action potentials recorded from SGNs show a significant decrease in the frequency of firing in Cav1.3(-/-) mice compared with wild-type (Cav1.3(+/+)) littermates. Although Cav1.3 is the designated L-type channel in neurons, whole-cell currents recorded in isolated SGNs from Cav1.3(-/-) mice showed a surprising remnant current with sensitivity toward the dihydropyridine (DHP) agonist and antagonist, and a depolarization shift in the voltage-dependent activation compared with that in the Cav1.3(+/+) mice. Indeed, direct measurement of the elementary properties of Ca(2+) channels, in Cav1.3(+/+) neurons, confirmed the existence of two DHP-sensitive single-channel currents, with distinct open probabilities and conductances. We demonstrate that the DHP-sensitive current in Cav1.3(-/-) mice is derived from Cav1.2 channel activity, providing for the first time, to our knowledge, functional data for the expression of Cav1.2 currents in neurons. Finally, using shRNA gene knockdown methodology, and histological analyses of SGNs from Cav1.2(+/-) and Cav1.3(+/-) mice, we were able to establish the differential roles of Cav1.2 and Cav1.3 in SGNs.
University of California, Davis, School of Medicine, Center for Neuroscience, Program in Communication Science, Davis, California 95618, Department of Pharmacology, Hebei Medical University, Shijiazhuang, China 050017.
Ping
P
Lv
University of California, Davis, School of Medicine, Center for Neuroscience, Program in Communication Science, Davis, California 95618.
Hyo Jeong
HJ
Kim
University of California, Davis, School of Medicine, Center for Neuroscience, Program in Communication Science, Davis, California 95618.
Jeong-Han
JH
Lee
University of California, Davis, School of Medicine, Center for Neuroscience, Program in Communication Science, Davis, California 95618.
Choong-Ryoul
CR
Sihn
University of California, Davis, School of Medicine, Center for Neuroscience, Program in Communication Science, Davis, California 95618.
Somayeh
S
Fathabad Gharaie
University of California, Davis, School of Medicine, Center for Neuroscience, Program in Communication Science, Davis, California 95618.
Atefeh
A
Mousavi-Nik
University of California, Davis, School of Medicine, Center for Neuroscience, Program in Communication Science, Davis, California 95618.
Wenying
W
Wang
Department of Medicine, Division of Cardiology, Duke University Medical Center, Durham, North Carolina 27710.
Hong-Gang
HG
Wang
Saint Louis University, School of Medicine, Department of Otolaryngology, Head-Neck Surgery, St. Louis, Missouri 63110, and.
Michael Anne
MA
Gratton
University of California, Davis, School of Medicine, Center for Neuroscience, Program in Communication Science, Davis, California 95618.
Karen J
KJ
Doyle
Department of Internal Medicine, Division of Cardiology, University of California, Davis, California 95616.
Xiao-Dong
XD
Zhang
Department of Internal Medicine, Division of Cardiology, University of California, Davis, California 95616, Northern California, Health Care System, Mather, California 95655.
Nipavan
N
Chiamvimonvat
University of California, Davis, School of Medicine, Center for Neuroscience, Program in Communication Science, Davis, California 95618, enyamoah@ucdavis.edu.
Ebenezer N
EN
Yamoah
D000200:Action Potentials / Q000187:drug effects / Q000235:genetics; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D020746:Calcium Channels, L-Type / Q000235:genetics / Q000378:metabolism*; D003051:Cochlea / Q000502:physiology; D005260:Female; D005786:Gene Expression Regulation / Q000187:drug effects / Q000235:genetics; D057809:HEK293 Cells; D006801:Humans; D066298:In Vitro Techniques; D008297:Male; D049990:Membrane Transport Modulators / Q000494:pharmacology; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D009474:Neurons / Q000378:metabolism*; D013136:Spiral Ganglion / Q000166:cytology*; D014404:Tubulin / Q000378:metabolism
C514350:CACNA1C protein, mouse; C485995:Cacna1d protein, mouse; D020746:Calcium Channels, L-Type; D049990:Membrane Transport Modulators; D014404:Tubulin; C462941:beta3 tubulin, mouse; D002118:Calcium
action potentials; calcium channels; deafness; hearing; neuronal degeneration; neuronal survival