|Institution:||University of New South Wales|
|Keywords:||Cerebellum; TRPC3; Alternative splicing|
|Full text PDF:||http://handle.unsw.edu.au/1959.4/54248|
Canonical transient receptor potential 3 (TRPC3) channels are nonselective cation channels from the TRPC family that are particularly important in Ca2+ homeostasis and signalling in neurons. These channels have multiple modes of activation, via a G-protein coupled receptor (GPCR) – phospholipase C (PLC) – diacylglycerol (DAG) pathway, as well as via intracellular store depletion and coupling to the inositol triphosphate (IP¬3) receptor. The TRPC3 channels are highly expressed in the brain and have diverse functions. In the cerebellum, TRPC3 has been shown to mediate neuroprotection or neurotoxicity, growth cone guidance, and neurotransmission related to motor coordination. This study focusses on the discovery and functional characterisation of a novel TRPC3 subunit splice variant, designated as TRPC3c. TRPC3c is formed by omission of a small exon (exon 9) which consists of 84 bases thatcodes for 28 amino acids. This exon codes for a significant portion of a regulatory domain known as the calmodulin - inositol triphosphate (IP3) receptor binding (CIRB) domain in the C-terminus. The TRPC3c splice variant is shown here to be widely expressed throughout the brain in various mammalian species including, mouse, rat, guinea pig and human. TRPC3c showed the highest expression level in the cerebellum in all these species. Functional characterisation of the recombinant TRPC3c channels by means of Ca2+ imaging and electrophysiology showed that this isoform has very high activity, with an increased channel opening rate compared to the formerly discovered TRPC3b isoform (wild-type). Our data suggests that this increased activity may be attributed to reduced sensitivity to intracellular [Ca2+], possibly due to altered interaction with intracellular regulators of the channels such as calmodulin. Given the high expression of the TRPC3c isoform in the cerebellum and its unusually high channel activity, it is likely that TRPC3c contributes significantly to Ca2+ and Na+ entry. TRPC3c may therefore have a crucial role in several cellular processes, including neuronal growth, survival, death, and neurotransmission.