Biology subjects

Campiglio, M.

Publications and source records attributed to Campiglio, M..

4 recordsLinked to original sources

bioRxiv2025

The expression level of CACNA1C-encoded CaV1.2 is a tipping point between promotion and inhibition of dendritic growth in neurons

The CACNA1C gene encodes the CaV1.2 L-type voltage-gated calcium channel, which plays a crucial role in neuronal signaling. CACNA1C is a risk gene for psychiatric conditions involving disruption of neuronal connectivity such as schizophrenia, autism, and bipolar disorders. While genomic studies are consistently reinforcing the notion of CACNA1C as an important locus related to these diseases, the role of CaV1.2 channels in determining neuronal architecture is incompletely understood. Several studies pinpoint the L-type current (ICaL) as regulator of dendritic arborization development. ICaL lays upstream of competing cellular mechanisms leading to both inhibition and promotion of dendritic growth. How signal selectivity is achieved remains an open question. Here, we report that ICaL-dependent dendritic development of murine cultured hippocampal neurons relies on CaV1.2 and is determined by an equilibrium between the level of CaV1.2 protein expression and ICaL activity. Indeed, increasing ICaL enhances dendritic complexity only when CaV1.2 expression level is reduced. In contrast, when channel levels are at baseline, the CaV1.2-dependent growing signal is overcome by the elevation of the dendritic growth inhibiting CaMKII signaling beyond basal conditions. These findings suggest that CaV1.2 expression level acts as a molecular switch between dendritic growing and inhibiting signals. Consequently, altered CaV1.2 expression during early development may alter neuronal structure, potentially impairing neural network formation and increasing susceptibility to psychiatric disorders. SIGNIFICANCE STATEMENTL-type voltage-gated calcium channels (L-VGCCs) allow calcium influx upon membrane depolarization. In neurons, L-VGCCs play a crucial role in regulating gene transcription, synaptic plasticity, and membrane excitability. Our data demonstrate that the L-VGCCs CaV1.2 isoform is a key regulator of early dendritic development. Calcium influx via CaV1.2 is necessary for proper dendritic growth under basal conditions. However, enhanced calcium currents boost dendritic growth only when channel expression levels are reduced. When the amount of CaV1.2 is at baseline, current stimulation antagonizes the growing process by upregulating the CaMKII signaling. Our findings suggest that the number of CaV1.2 available determines whether channel activity leads to aberrant dendritic arborization by sizing the recruitment of growth inhibiting CaMKII cascade.

neuroscience↗

bioRxiv2025

A bi-directional binding site linking the α2δ-1 subunit to the intrinsic speed control process in VSD I of voltage-gated calcium channels

Voltage-gated calcium channels communicate electrical signals in membranes of excitable cells into cellular responses like secretion of hormones and neurotransmitters, or the contraction of heart and skeletal muscle cells. Their activation properties are tuned to match their specific functions. Consequently, the different members of the calcium channel family activate over a wide range of voltages and with greatly differing speeds. The skeletal muscle CaV1.1 and the cardiac/neuronal CaV1.2 represent two structurally closely related channels with particularly slow and fast activation kinetics, respectively. Both channel paralogs associate with the auxiliary calcium channel subunit 2{delta}-1, which is a known regulator of activation properties. By expressing CaV1.1 and CaV1.2 with and without 2{delta}-1 in a new double-knockout muscle cell line, we demonstrate that 2{delta}-1 regulates activation kinetics of the two channels in opposite directions. Molecular dynamics simulation revealed a string of charged amino acids connecting 2{delta}-1 to the intrinsic speed-control mechanism of voltage-sensing domain I (VSD I) in CaV1.1. Charge-neutralizing mutations of any of these charged amino acids abolished the 2{delta}-1 modulation and accelerated current kinetics. Together, these results reveal the molecular mechanism by which the 2{delta}-1 subunit regulates the intrinsic speed-control mechanism in the VSD I of CaV1.1 calcium channels.

biophysics↗

bioRxiv2021

Calcium current modulation by the γ1 subunit depends on alternative splicing of CaV1.1

The skeletal muscle voltage-gated calcium channel (CaV1.1) primarily functions as voltage sensor for excitation-contraction coupling. Conversely, its ion-conducting function is modulated by multiple mechanisms within the pore-forming 1S subunit and the auxiliary 2{delta}-1 and {gamma}1 subunits. Particularly, developmentally regulated alternative splicing of exon 29, which inserts 19 amino acids in the extracellular IVS3-S4 loop of CaV1.1a, greatly reduces the current density and shifts the voltage-dependence of activation to positive potentials outside the physiological range. We generated a new HEK293-cell line stably expressing 2{delta}-1, {beta}3, and STAC3. When the adult (CaV1.1a) and the embryonic (CaV1.1e) splice variants were expressed in these cells, the difference in the voltage-dependence of activation observed in muscle cells was reproduced, but not the reduced current density of CaV1.1a. Only when we further co-expressed the {gamma}1 subunit, the current density of CaV1.1a, but not of CaV1.1e, was reduced by >50 %. In addition, {gamma}1 caused a shift of the voltage-dependence of inactivation to negative voltages in both variants. Thus, the current-reducing effect of {gamma}1, but not its effect on inactivation, is specifically dependent on the inclusion of exon 29 in CaV1.1a. Molecular structure modeling revealed several direct ionic interactions between oppositely charged residues in the IVS3-S4 loop and the {gamma}1 subunit. However, substitution of these residues by alanine, individually or in combination, did not abolish the {gamma}1-dependent reduction of current density, suggesting that structural rearrangements of CaV1.1a induced by inclusion of exon 29 allosterically empower the {gamma}1 subunit to exert its inhibitory action on CaV1.1 calcium currents. SummaryEl Ghaleb et al. analyzed the effects of the {gamma}1 subunit on current properties and expression of the adult (CaV1.1a) and embryonic (CaV1.1e) calcium channel splice variants, demonstrating that {gamma}1 reduces the current amplitude in a splicing-dependent manner.

physiology↗

bioRxiv2019

Presynaptic α2δ subunits are key organizers of glutamatergic synapses

In nerve cells the genes encoding for 2{delta} subunits of voltage-gated calcium channels (VGCCs) have been linked to synaptic functions and neurological disease. Here we show that 2{delta} subunits are essential for the formation and organization of glutamatergic synapses. Using a cellular 2{delta} subunit triple loss-of-function model, we demonstrate a failure in presynaptic differentiation associated with the downscaling of postsynaptic AMPA receptors and the postsynaptic density. The role of 2{delta} isoforms as synaptic organizers is highly redundant, as each individual 2{delta} isoform can rescue presynaptic calcium channel trafficking and expression of synaptic proteins. Mutating the MIDAS site in 2{delta}-2 dissociates rescuing presynaptic synapsin expression from calcium channel trafficking, suggesting that the regulatory role of 2{delta} subunits is independent from its role as a calcium channel subunit. Our findings influence the current view on excitatory synapse formation. Firstly, our study suggests that postsynaptic differentiation is secondary to presynaptic differentiation. Secondly, the dependence of presynaptic differentiation on 2{delta} implicates 2{delta} subunits as potential nucleation points for the organization of synapses. Finally, our results suggest that 2{delta} subunits act as trans-synaptic organizers of glutamatergic synapses, thereby aligning the synaptic active zone with the postsynaptic density.

neuroscience↗