Disease relevance of TRPC3

• These results suggest that TRPC3 may be an important therapeutic target in inflammatory airway diseases such as asthma and chronic obstructive pulmonary disease [1].
• Cleavage of VAMP2 with tetanus toxin (TeNT) did not prevent delivery of TRPC3 to the plasma membrane region but reduced its surface expression [2].
• In lung tissues and PASMC from IPAH patients, the mRNA and protein expression of TRPC3 and -6 were much higher than in those from normotensive or secondary pulmonary hypertension patients [3].
• TRPC3 and TRPC6 are essential for angiotensin II-induced cardiac hypertrophy [4].
• We conclude that, in prostate cancer epithelial cells, alpha1-ARs and m1-AChRs are functionally coupled to Ca2+-permeable DAG-gated cationic channels, for which TRPC1 and TRPC3 are the most likely candidates [5].

High impact information on TRPC3

• TRP-3 is initially localized in intracellular vesicles, and then translocates to the plasma membrane during sperm activation [6].
• Expression in COS cells of two full-length cDNAs encoding human trp homologs, Htrp1 and Htrp3, increased CCE [7].
• Although hTRPC3, the closest structural relative of hTRPC6, is activated in the same way, TRPCs 1, 4 and 5 and the vanilloid receptor subtype 1 are unresponsive to the lipid mediator [8].
• Importantly, carbachol, not thapsigargin, increased surface expression of TRPC3 that was attenuated by TeNT and not by BAPTA [2].
• Further, endogenous and exogenously expressed TRPC3 colocalized and coimmunoprecipitated with SNARE proteins in neuronal and epithelial cells [2].

Biological context of TRPC3

• Importantly, direct activation of TRPC3 channels by diacylglycerol was also blocked by BTP2 (IC50 approximately 0.3 microM) [9].
• By immunocytochemistry, TRPC3 and TRPC4 were localised to cytotrophoblast cells in first trimester placentas and to the syncytiotrophoblast in term placentas [10].
• The effects of TNF-alpha treatment on SOCE and agonist-induced intracellular Ca(2+) concentration responses were attenuated using small interfering RNA transfection, which knocked down TRPC3 expression [1].
• VAMP2-dependent exocytosis regulates plasma membrane insertion of TRPC3 channels and contributes to agonist-stimulated Ca2+ influx [2].
• Point mutations at two consensus PKG phosphorylation sites (T11A and S263Q) of TRPC3 channel markedly reduced the inhibitory effect of cGMP [11].

Anatomical context of TRPC3

• Immunofluorescence microscopy demonstrated localization of TRPC1, TRPC3, and TRPC4 to the PMN cell membrane and their internalization after cytoskeletal reorganization by calyculin A (CalyA) [12].
• Using the T3-65 clonal HEK293 cell line stably expressing TRPC3 channels, TRPC3-mediated Sr2+ entry activated by muscarinic receptors was also blocked by BTP2 with an IC50 of <0.3 microM [9].
• Our data provide the initial step toward understanding the molecular nature of endogenous Ca2+ channels participating in T-cell activation and put forward TRPC3 as a new target for modulating the immune response [13].
• Endogenously and exogenously expressed TRPC3 was localized apically in polarized Madin-Darby canine kidney cells (MDCK) and salivary gland epithelial cells [14].
• Most importantly, (i) TRPC3 was detected in the apical region of rat submandibular gland ducts, whereas TRPC6 was present in apical as well as basolateral regions of ducts and acini; and (ii) OAG stimulated Ca2+ influx into dispersed ductal cells [14].

Associations of TRPC3 with chemical compounds

• What is not known is the step at which src acts on TRPC3 and whether the role for tyrosine kinases in ROCE or SOCE is a general phenomenon [15].
• It encodes a putative variant of the C3-type TRPC (transient receptor potential channel) that differs from the previously cloned murine TRPC3 cDNA in that it has a 5' extension stemming from inclusion of an additional exon (exon 0) [16].
• Whereas whole-cell carbachol-induced TRPC3 current was blocked by 3 microM BTP2, single TRPC3 channel recordings revealed persistent short openings suggesting BTP2 reduces the open probability of the channel rather than its pore properties [9].
• The suppression of either TRPC3 or TRPC7, but not TRPC1, induced a high Ba(2+) leak flux that was inhibited by 2-APB and SKF96365, suggesting that the influx is via leaky store-operated channels [17].
• The distributions of TRPC3 and TRPC6 between soluble and membrane fractions were not affected by methyl-beta-cyclodextrin treatment [18].

Physical interactions of TRPC3

• Conversely, TRPC1 co-immunoprecipitated with TRPC3 [19].
• Glutathione S-transferase pull-down experiments revealed that NCX1 interacts with the cytosolic C terminus of TRPC3 [20].
• Conformational coupling with the inositol 1,4,5-trisphosphate (IP3) receptor has been suggested as a possible mechanism of activation of TRPC3 channels and a region in the C terminus of TRPC3 has been shown to interact with the IP3 receptor as well as calmodulin (calmodulin/IP3 receptor-binding (CIRB) region) [21].

Enzymatic interactions of TRPC3

• The C-terminal half of the PLC-gamma split PH domain has been implicated to interact directly with the TRPC3 calcium channel, thereby providing a direct coupling mechanism between PLC-gamma and agonist-induced calcium entry [22].

Co-localisations of TRPC3

• TRPC3 and -C6 colocalized with aquaporin-2, but not with the Na(+)/Ca(2+) exchanger or peanut lectin [23].

Regulatory relationships of TRPC3

• TRPC5 channels transiently expressed in HEK293 cells were blocked by BTP2 in the same range as TRPC3 [9].
• Normal human PASMC expressed multiple canonical TRP (TRPC) isoforms; TRPC6 was highly expressed and TRPC3 was minimally expressed [3].
• VEGF is also able to activate heterologously expressed TRPC3/6 channels through VEGFR2 [24].
• 4) Expression of dominant-negative TRPC4 proteins suppressed TRPC3-related channel activity in the HEK293 expression system and in native endothelial cells [25].
• Based on these data, we conclude that expression of TRPC3 is tightly regulated during muscle cell differentiation and propose that functional interaction between TRPC3 and RyR1 may regulate the gain of SR Ca(2+) release independent of SR Ca(2+) load [26].
• Substitution of Tyr(226) alone with phenylalanine significantly reduced the Epo-stimulated increase in [Ca(2+)](i) but not the association of PLCgamma with TRPC3 [27].

Other interactions of TRPC3

• Direct activation of human TRPC6 and TRPC3 channels by diacylglycerol [8].
• We show that PKD2 can directly associate with TRPC1 but not TRPC3 in transfected cells and in vitro [28].
• However, mutual swap of VP and IP in TRPC3 and TRPC5 did not alter the association or the selectivity of the channels for their respective immunophilin binding partner [29].
• Regulation of Ca2+ entry is a key process for lymphocyte activation, and TRP channels may both increase Ca2+ influx (such as TRPC3) or decrease Ca2+ influx through membrane depolarization (such as TRPM4) [30].
• NCX1 immunoreactivity was detectable in HEK293 as well as in TRPC3-overexpressing HEK293 cells, and reduction of extracellular Na(+) after Na(+) loading with monensin resulted in significant rises in intracellular free Ca(2+) (Ca(2+)(i)) of HEK293 cells [20].
• Epo-R and phospholipase Cgamma associated with TRPC3, and these interactions were significantly reduced with TRPC6 and TRPC3-C6C chimeras [31].

Analytical, diagnostic and therapeutic context of TRPC3

• Immunoprecipitation of TRPC1 pulled down TRPC3 but not TRPC4 [19].
• From Western blotting, TRPC3 and TRPC6 proteins were detected in term, but not in first trimester, placentas, while TRPC1 protein was not detected [10].
• TRPC1 and TRPC6 mRNA were more than fivefold increased in cells isolated after organ culture, whereas TRPC3 was decreased [32].
• In HEK-293 cells stably transfected with a 323-bp Htrp3 antisense construct (Htrp3AS), Northern blot analysis revealed that the expression of a 4-kb transcript was dramatically suppressed in comparison to that observed in cells stably transfected with a short Htrp3 sense construct (Htrp3S) [33].
• We demonstrate by site-directed mutagenesis that a single site containing Ser(712) and conserved among all members of the TRPC family is essential for protein kinase C-mediated negative regulation of TRPC3 [34].

References