VEGA 2/0107/16

Principal Investigator: Ľubica Lacinová

Duration: January 2016 – December 2018
Coordinating Organization: Centre of Biosciences – Institute of Molecular Physiology and Genetics SAS, Bratislava

Annotation:

Neurotransmission controlled by CaV2.2 or N-type calcium channels plays a major role in chronic and neuropathic pain which is a major clinical, social and economic problem. Ziconotide is the only one drug specifically targeting CaV2.2 channel. It is delivered intrathecally leaving demand for an oral drug open. Ion channels form macromolecular signaling complexes with a variety of interacting proteins and stabilization or disruption of such interactions may be a base for a novel therapeutic strategy. Modified yeast-two-hybrid assay identified proteins RTN1, SLC38A1, Ptgds, TMEM 223, and Grina as putative interaction partners of the CaV2.2 channels. These proteins are expressed predominantly or solely in neurons and several neuromodulatory functions of these proteins were described. We hypothesize that they may modulate CaV2.2 channels, as well. Our aim is to describe functional mechanisms and/or intracellular pathways involved in the interaction between CaV2.2 channels and listed interacting proteins.

Kyewords:

N-type calcium channels, intracellular calcium, neuronal excitability, chronic pain, interactome, two-pore channels

Objectives:

Main aim of our project is to characterize modulation of the neuronal CaV2.2 calcium channel by five proteins: RTN1, SLC38A1, Ptgds, TMEM 223, and Grina. All these proteins were identified as putative interaction partners of the CaV2.2 protein by a modified yeast two-hybrid assay (YTH). A modified YTH system used a split-ubiquitin which allowed the detection of protein-protein interactions within or close to plasma membranes. We will concentrate on three aspect of the CaV2.2channel interactome:

1. Regulation of voltage- and time-dependent activity of the CaV2.2 channel itself.

Main role of CaV2.2 channels is generation of large but temporally precise calcium influx into presynaptic neurons. Even minor change in the channel gating may translate into significant modulation of synaptic transmission. We will characterize voltage dependence and kinetics of activation and inactivation, cumulative inactivation evoked by high-frequency trains of rectangular depolarizing pulses and/or action-potential-like waveforms in the absence and presence of each putative interacting protein. Further, we will estimate channel’s opening probability from a relation between maximal ionic and gating currents.

2. Modulation of a downstream regulatory pathways.

We will investigate modulation of CaV2.2 channels activity by intracellular messengers and/or G-proteins in the absence or presence of each interacting protein.

3. Regulation of a endolysosomal two pore cation channels (TPC) which may involve an interplay with the plasmalemmal CaV2.2 channel.

TPC are less characterized intracellular cation channels who’s activity is modulated by plasmalemmal calcium influx. We will use chimeric channels constructed from parts of CaV3.1 and TPC expressed in the HEK 293 cells as a model for characterization of their electrophysiological properties, e.g., putative voltage-dependence of activation/inactivation and kinetics of those processes. Furthermore, we will define the ion selectivity of the TPC1 pore.

Publications: