Inositol 1,4,5-trisphosphate activates TRPC3 channels to cause extracellular Ca2+ influx in airway smooth muscle cells.

Transient receptor potential-3 (TRPC3) channels play a predominant role in forming nonselective cation channels (NSCCs) in airway smooth muscle cells (ASMCs) and are significantly increased in their activity and expression in asthmatic ASMCs. To extend these novel findings, we have explored the regulatory mechanisms that control the activity of TRPC3 channels. Our data for the first time reveal that inositol 1,4,5-trisphosphate (IP3), an important endogenous signaling molecule, can significantly enhance the activity of single NSCCs in ASMCs. The analog of diacylglycerol (DAG; another endogenous signaling molecule), 1-oleyl-2-acetyl-sn-glycerol (OAG), 1-stearoyl-2-arachidonoyl-sn-glycerol (SAG), and 1-stearoyl-2-linoleoyl-sn-glycerol (SLG) all augment NSCC activity. The effects of IP3 and OAG are fully abolished by lentiviral short-hairpin (sh)RNA-mediated TRPC3 channel knockdown (KD). The stimulatory effect of IP3 is eliminated by heparin, an IP3 receptor (IP3R) antagonist that blocks the IP3-binding site, but not by xestospongin C, the IP3R antagonist that has no effect on the IP3-binding site. Lentiviral shRNA-mediated KD of IP3R1, IP3R2, or IP3R3 does not alter the excitatory effect of IP3. TRPC3 channel KD greatly inhibits IP3-induced increase in intracellular Ca(2+) concentration. IP3R1 KD produces a similar inhibitory effect. TRPC3 channel and IP3R1 KD both diminish the muscarinic receptor agonist methacholine-evoked Ca(2+) responses. Taking these findings together, we conclude that IP3, the important intracellular second messenger, may activate TRPC3 channels to cause extracellular Ca(2+) influx, in addition to opening IP3Rs to induce intracellular Ca(2+) release. This novel extracellular Ca(2+) entry route may play a significant role in mediating IP3-mediated numerous cellular responses in ASMCs and other cells.

Song T ，Hao Q ，Zheng YM ，Liu QH ，Wang YX ... -  《-》

IP3 constricts cerebral arteries via IP3 receptor-mediated TRPC3 channel activation and independently of sarcoplasmic reticulum Ca2+ release.

Xi Q ，Adebiyi A ，Zhao G ，Chapman KE ，Waters CM ，Hassid A ，Jaggar JH ... -  《-》

TRPC3-mediated Ca(2+) entry contributes to mouse airway smooth muscle cell proliferation induced by lipopolysaccharide.

Airway remodeling is a histopathological hallmark of chronic respiratory diseases that includes airway smooth muscle cell (ASMC) proliferation. Canonical transient receptor potential channel-3 (TRPC3)-encoded nonselective cation channels (NSCCs) are important native constitutively active channels that play significant roles in physiological and pathological conditions in ASMCs. Lipopolysaccharides (LPSs), known as lipoglycans and endotoxin, have been proven to be inducers of airway remodeling, though the mechanisms remain unclear. We hypothesized that TRPC3 is important in LPS-induced airway remodeling by regulating ASMC proliferation. To test this hypothesis, mouse ASMCs were cultured with or without LPS for 48h. Cell viability, TRPC3 protein expression, NSCC currents and changes in intracellular calcium concentration ([Ca(2+)]i) were then analyzed using an MTT assay, western blotting, whole-cell patch clamp and calcium imaging, respectively. The results showed that LPS treatment significantly induced ASMC proliferation, up-regulation of TRPC3 protein expression and enhancement of NSCC currents, resting [Ca(2+)]i and ACh-elicited changes in [Ca(2+)]i. TRPC3 blocker Gd(3+), TRPC3 blocking antibody or TRPC3 gene silencing by siRNA significantly inhibited LPS-induced up-regulation of TRPC3 protein, enhancement of NSCC currents, resting [Ca(2+)]i and ACh-elicited changes in [Ca(2+)]i, eventually inhibiting LPS-induced ASMCproliferation. These results demonstrated that TRPC3-mediated Ca(2+) entry contributed to LPS-induced ASMC proliferation and identified TRPC3 as a possible key target in airway remodeling intervention.

Chen XX ，Zhang JH ，Pan BH ，Ren HL ，Feng XL ，Wang JL ，Xiao JH ... -  《-》

Receptor-operated Ca2+ entry mediated by TRPC3/TRPC6 proteins in rat prostate smooth muscle (PS1) cell line.

Prostate smooth muscle cells predominantly express alpha1-adrenoceptors (alpha1-AR). alpha1-AR antagonists induce prostate smooth muscle relaxation and therefore they are useful therapeutic compounds for the treatment of benign prostatic hyperplasia symptoms. However, the Ca(2+) entry pathways associated with the activation of alpha1-AR in the prostate have yet to be elucidated. In many cell types, mammalian homologues of transient receptor potential (TRP) genes, first identified in Drosophila, encode TRPC (canonical TRP) proteins. They function as receptor-operated channels (ROCs) which are involved in various physiological processes such as contraction, proliferation, apoptosis, and differentiation. To date, the expression and function of TRPC channels have not been studied in prostate smooth muscle. In fura-2 loaded PS1 (a prostate smooth muscle cell line) which express endogenous alpha1A-ARs, alpha-agonists epinephrine (EPI), and phenylephrine (PHE) induced Ca(2+) influx which depended on the extracellular Ca(2+) and PLC activation but was independent of PKC activation. Thus, we have tested two membrane-permeable analogues of diacylglycerol (DAG), oleoyl-acyl-sn-glycerol (OAG) and 1,2-dioctanoyl-sn-glycerol (DOG). They initiated Ca(2+) influx whose properties were similar to those induced by the alpha-agonists. Sensitivity to 2-aminoethyl diphenylborate (2-APB), SKF-96365 and flufenamate implies that Ca(2+)-permeable channels mediated both alpha-agonist- and OAG-evoked Ca(2+) influx. Following the sarcoplasmic reticulum (SR) Ca(2+) store depletion by thapsigargin (Tg), a SERCA inhibitor, OAG and PHE were both still able to activate Ca(2+) influx. However, OAG failed to enhance Ca(2+) influx when added in the presence of an alpha-agonist. RT-PCR and Western blotting performed on PS1 cells revealed the presence of mRNAs and the corresponding TRPC3 and TRPC6 proteins. Experiments using an antisense strategy showed that both alpha-agonist- and OAG-induced Ca(2+) influx required TRPC3 and TRPC6, whereas the Tg-activated ("capacitative") Ca(2+) entry involved only TRPC3 encoded protein. It may be thus concluded that PS1 cells express TRPC3 and TRPC6 proteins which function as receptor- and store-operated Ca(2+) entry pathways.

Thebault S ，Zholos A ，Enfissi A ，Slomianny C ，Dewailly E ，Roudbaraki M ，Parys J ，Prevarskaya N ... -  《JOURNAL OF CELLULAR PHYSIOLOGY》

Regulation of canonical transient receptor potential (TRPC) channel function by diacylglycerol and protein kinase C.

Venkatachalam K ，Zheng F ，Gill DL 《JOURNAL OF BIOLOGICAL CHEMISTRY》