TRPC Channels Activated by G Protein-Coupled Receptors Drive Ca2+ Dysregulation Leading to Secondary Brain Injury in the Mouse Model

Jasneet Parmar; Georg von Jonquieres; Nagarajesh Gorlamandala; Brandon Chung; Amanda J Craig; Jeremy L Pinyon; Lutz Birnbaumer; Matthias Klugmann; Andrew J Moorhouse; John M Power; Gary D Housley

doi:10.1007/s12975-023-01173-1

TRPC Channels Activated by G Protein-Coupled Receptors Drive Ca²⁺ Dysregulation Leading to Secondary Brain Injury in the Mouse Model

Transl Stroke Res. 2023 Jul 18. doi: 10.1007/s12975-023-01173-1. Online ahead of print.

Affiliations

¹ Translational Neuroscience Facility and Department of Physiology, School of Biomedical Sciences, UNSW Sydney, Sydney, NSW, 2052, Australia.
² Institute of Biomedical Research (BIOMED), Pontifical Catholic University of Argentina, Av. A Moreau de Justo 1300, C1107AFF, Buenos Aires CABA, Argentina.
³ Laboratory of Signal Transduction, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina, 27709, USA.
⁴ Translational Neuroscience Facility and Department of Physiology, School of Biomedical Sciences, UNSW Sydney, Sydney, NSW, 2052, Australia. g.housley@unsw.edu.au.

PMID: 37462831
DOI: 10.1007/s12975-023-01173-1

Abstract

Canonical transient receptor potential (TRPC) non-selective cation channels, particularly those assembled with TRPC3, TRPC6, and TRPC7 subunits, are coupled to G_αq-type G protein-coupled receptors for the major classes of excitatory neurotransmitters. Sustained activation of this TRPC channel-based pathophysiological signaling hub in neurons and glia likely contributes to prodigious excitotoxicity-driven secondary brain injury expansion. This was investigated in mouse models with selective Trpc gene knockout (KO). In adult cerebellar brain slices, application of glutamate and the class I metabotropic glutamate receptor agonist (S)-3,5-dihydroxyphenylglycine to Purkinje neurons expressing the GCaMP5g Ca²⁺ reporter demonstrated that the majority of the Ca²⁺ loading in the molecular layer dendritic arbors was attributable to the TRPC3 effector channels (Trpc3^KO compared with wildtype (WT)). This Ca²⁺ dysregulation was associated with glutamate excitotoxicity causing progressive disruption of the Purkinje cell dendrites (significantly abated in a GAD67-GFP-Trpc3^KO reporter brain slice model). Contribution of the G_αq-coupled TRPC channels to secondary brain injury was evaluated in a dual photothrombotic focal ischemic injury model targeting cerebellar and cerebral cortex regions, comparing day 4 post-injury in WT mice, Trpc3^KO, and Trpc1/3/6/7 quadruple knockout (Trpc^QKO), with immediate 2-h (primary) brain injury. Neuroprotection to secondary brain injury was afforded in both brain regions by Trpc3^KO and Trpc^QKO models, with the Trpc^QKO showing greatest neuroprotection. These findings demonstrate the contribution of the G_αq-coupled TRPC effector mechanism to excitotoxicity-based secondary brain injury expansion, which is a primary driver for mortality and morbidity in stroke, traumatic brain injury, and epilepsy.

Keywords: AAVrh20-GCaMP5g genetically encoded Ca2+ reporter; GAD67-GFP-Trpc3 KO); Glutamate excitotoxicity; Neuroprotection; Photothrombotic focal ischemic brain injury model; Trpc knockout mouse models (Trpc3; Trpc1/3/6/7.