Ca2+ entry into neurons is facilitated by cooperative gating of clustered CaV1.3 channels

Abstract

CaV1.3 channels regulate excitability in many neurons. As is the case for all voltage-gated channels, it is widely assumed that individual CaV1.3 channels behave independently with respect to voltage-activation, open probability, and facilitation. Here, we report the results of super-resolution imaging, optogenetic, and electrophysiological measurements that refute this long-held view. We found that the short channel isoform (CaV1.3S), but not the long (CaV1.3L), associates in functional clusters of two or more channels that open cooperatively, facilitating Ca2+ influx. CaV1.3S channels are coupled via a C-terminus-to-C-terminus interaction that requires binding of the incoming Ca2+ to calmodulin (CaM) and subsequent binding of CaM to the pre-IQ domain of the channels. Physically-coupled channels facilitate Ca2+ currents as a consequence of their higher open probabilities, leading to increased firing rates in rat hippocampal neurons. We propose that cooperative gating of CaV1.3S channels represents a mechanism for the regulation of Ca2+ signaling and electrical activity.DOI: http://dx.doi.org/10.7554/eLife.15744.001

Nitric Oxide–Dependent Feedback Loop Regulates Transient Receptor Potential Vanilloid 4 (TRPV4) Channel Cooperativity and Endothelial Function in Small Pulmonary Arteries

“…Coupling coefficients for the coupling among TRPV4 channels at a cluster were determined using a coupled Markov chain model in MATLAB, as previously described 5, 31, 32, 33, 34. [F‐F 0 ]/F 0 traces showing steady baseline (ie, at least 30 s duration) were selected for analyzing the cooperative gating of TRPV4 channels.…”

β‐adrenergic‐mediated dynamic augmentation of sarcolemmal CaV1.2 clustering and co‐operativity in ventricular myocytes

“…Physical interactions between Ca V 1.2 channels were assayed using BiFC as described previously (Dixon et al, 2015;Moreno et al, 2016). Briefly, this protein-protein interaction assay was performed in tsA-201 cells transfected with 'split venus' tagged channels as described above [Ca V 1.2-VC155 and Ca V 1.2-VN155(I152L)].…”

“…1). We have previously used this approach to assay the Ca 2+ and CaM-dependence of Ca V 1.2-Ca V 1.2 interactions in tsA201 cells (Dixon et al, 2015;Moreno et al, 2016). For this, we generated two fusion proteins, Ca V 1.2-VC155 and Ca V 1.2-VN155(I152L), by fusing the N-or C-terminal fragment of the venus fluorescent protein (FP) onto the J Physiol 597.8 C-terminal of the Ca V 1.2 α 1c subunit.…”

“…Thus, expression of FP-tagged channels in cardiomyocytes to monitor their trafficking and dynamics presents a technical challenge. We have previously demonstrated successful transduction of mouse cardiomyocytes in vivo with various FP-tagged constructs using retro-orbital injections of AAV9 (Dixon et al, 2015;Drum et al, 2016;Moreno et al, 2016). This approach allows us to circumvent the need to culture the cells and lets the transduction proceed in vivo.…”

Modulation of Function, Structure and Clustering of K+ Channels by Lipids: Lessons Learnt from KcsA

“…Experimental data from other ion channels of excitable membranes, such as those in the heart and the nervous system, including the mammalian brain, also exhibit cooperative properties modulated by lipids, which are suggestive of clustering processes similar to that in KcsA [93][94][95][96][97][98][99][100][101][102][103]. This is to conclude that lipid-dependent processes such as those found in the KcsA model could be present in many other membrane proteins, including different ion channels.…”