Functional Charaterization of Zebrafish Transient Receptor Potential Melastatin 2

Abstract

Transient Receptor Potential Canonical 3 (TRPC3) channels have been demonstrated to underlie a slow excitatory postsynaptic current (sEPSC) that is coupled to the activation of type-1 metabotropic glutamate receptor (mGluR1) by glutamate release at the parallel fiber -Purkinje cell synapses of the cerebellum. On the other hand, Purkinje neurons receive extensive inhibitory synaptic inputs from interneurons located in the molecular layer of cerebellar cortex and GABA B receptors (GABA B Rs) are expressed on the dendrites of Purkinje cells and often co-localized with mGluR1. It has been shown that activation of postsynaptic GABA B Rs potentiates mGluR1-coupled sEPSCs in Purkinje cells, but the underlying molecular mechanism remains elusive. Here we report that the potentiation of mGluR1-coupled sEPSCs in Purkinje cells by stimulating postsynaptic GABA B Rs was completely absent in TRPC3 knockout mice, but persistent in TRPC1-, TRPC4-and TRPC1/4/5/6knockout mice, suggesting that TRPC3 is the only TRPC isoform that mediates the potentiation. Moreover, our results indicate that the potentiation was a pure postsynaptic event because it was not affected by blocking neurotransmission with tetrodotoxin. Furthermore, we found that the potentiation was blocked by antagonists of either GABA B Rs or mGluR1, suggesting that it may originate directly from the integration of synaptic signals at the receptor level and the strengthened signal was mainly mediated by mGluR1-TRPC3 coupling instead of any other pathways involved in GABA B R signaling. Since mGluR1-TRPC3 coupling is essential in cerebellar long-term depression, synapse elimination, and motor coordination, our findings that TRPC3 is also responsible for the synaptic integration of GABA B R-mediated inputs may suggest a novel mechanism that underlies essential cerebellar functions, such as motor learning.

Structures and gating mechanism of human TRPM2

“…In addition to sensing Ca 2+ and ADPR, hs TRPM2 has been shown to sense body temperature to limit the fever response (11, 12). By contrast, dr TRPM2 lacks intersubunit interactions (28) and does not respond to heat or pH (36). We speculate that higher temperature, in the form of enhanced thermal motion, may overcome the intersubunit interactions in hs TRPM2 to modulate gating.…”

Ligand recognition and gating mechanism through three ligand-binding sites of human TRPM2 channel

“…Human TRPM2 ( hs TRPM2) has several functional properties different from those of dr TRPM2 and invertebrate TRPM2, including temperature sensitivity and desensitization rate (Nam Tran et al, 2018; Iordanov et al, 2019). A recent publication suggested that hs TRPM2 does not bind ADPR in the MHR1/2 domain and that its activation is rather driven by ADPR binding in the NUDT9-H domain (Wang et al, 2018).…”