Journal article
Splicing of an automodulatory domain in Cav1.4 Ca2+ channels confers distinct regulation by calmodulin
The Journal of general physiology, Vol.150(12), pp.1676-1687
12/03/2018
DOI: 10.1085/jgp.201812140
PMCID: PMC6279360
PMID: 30355583
Abstract
Ca2+ influx through Cav1.4 L-type Ca2+ channels supports the sustained release of glutamate from photoreceptor synaptic terminals in darkness, a process that is critical for vision. Consistent with this role, Cav1.4 exhibits weak Ca2+-dependent inactivation (CDI)—a negative feedback regulation mediated by Ca2+-bound calmodulin (CaM). CaM binds to a conserved IQ domain in the proximal C-terminal domain of Cav channels, but in Cav1.4, a C-terminal modulatory domain (CTM) disrupts interactions with CaM. Exon 47 encodes a portion of the CTM and is deleted in a Cav1.4 splice variant (Cav1.4Δex47) that is highly expressed in the human retina. Cav1.4Δex47 exhibits CDI and enhanced voltage-dependent activation, similar to that caused by a mutation that is associated with congenital stationary night blindness type 2, in which the CTM is deleted (K1591X). The presence of CDI and very negative activation thresholds in a naturally occurring variant of Cav1.4 are perplexing considering that these properties are expected to be maladaptive for visual signaling and result in night blindness in the case of K1591X. Here we show that Cav1.4Δex47 and K1591X exhibit fundamental differences in their regulation by CaM. In Cav1.4Δex47, CDI requires both the N-terminal (N lobe) and C-terminal (C lobe) lobes of CaM to bind Ca2+, whereas CDI in K1591X is driven mainly by Ca2+ binding to the C lobe. Moreover, the CaM N lobe causes a Ca2+-dependent enhancement of activation of Cav1.4Δex47 but not K1591X. We conclude that the residual CTM in Cav1.4Δex47 enables a form of CaM N lobe regulation of activation and CDI that is absent in K1591X. Interaction with the N lobe of CaM, which is more sensitive to global elevations in cytosolic Ca2+ than the C lobe, may allow Cav1.4Δex47 to be modulated by a wider range of synaptic Ca2+ concentrations than K1591X; this may distinguish the normal physiological function of Cav1.4Δex47 from the pathological consequences of K1591X.
Details
- Title: Subtitle
- Splicing of an automodulatory domain in Cav1.4 Ca2+ channels confers distinct regulation by calmodulin
- Creators
- Brittany Williams - Department of Molecular Physiology and Biophysics, University of Iowa, Iowa City, IA, Interdisciplinary Graduate Program in Neuroscience, University of Iowa, Iowa City, IA, Iowa Neuroscience Institute, University of Iowa, Iowa City, IAFrançoise Haeseleer - Department of Physiology and Biophysics, University of Washington, Seattle, WAAmy Lee - Department of Molecular Physiology and Biophysics, University of Iowa, Iowa City, IA, Interdisciplinary Graduate Program in Neuroscience, University of Iowa, Iowa City, IA, Iowa Neuroscience Institute, University of Iowa, Iowa City, IA, Department of Otolaryngology Head-Neck Surgery, University of Iowa, Iowa City, IA, Department of Neurology, University of Iowa, Iowa City, IA
- Resource Type
- Journal article
- Publication Details
- The Journal of general physiology, Vol.150(12), pp.1676-1687
- DOI
- 10.1085/jgp.201812140
- PMID
- 30355583
- PMCID
- PMC6279360
- NLM abbreviation
- J Gen Physiol
- ISSN
- 0022-1295
- eISSN
- 1540-7748
- Grant note
- DOI: 10.13039/100000002, name: National Institutes of Health, award: DC009433, NS084190, EY026817, EY026477; name: Neuroscience Training Program, award: T32 NS007421; name: Carver Research Program of Excellence; DOI: 10.13039/100008893, name: University of Iowa, award: R25GM058939
- Language
- English
- Date published
- 12/03/2018
- Academic Unit
- Molecular Physiology and Biophysics
- Record Identifier
- 9984071795402771
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