TRPC1 Associates With BK _Ca Channel to Form a Signal Complex in Vascular Smooth Muscle Cells

Abstract

Abstract-TRPC1 (transient receptor potential canonical 1) is a Ca 2ϩ -permeable cation channel involved in diverse physiological function. TRPC1 may associate with other proteins to form a signaling complex, which is crucial for channel function. In the present study, we investigated the interaction between TRPC1 and large conductance Ca 2ϩ -sensitive K ϩ channel (BK Ca ). With the use of potentiometric fluorescence dye DiBAC 4 (3), we found that store-operated Ca 2ϩ influx resulted in membrane hyperpolarization of vascular smooth muscle cells (VSMCs). The hyperpolarization was inhibited by an anti-TRPC1 blocking antibody T1E3 and 2 BK Ca channel blockers, charybdotoxin and iberiotoxin. These data were confirmed by sharp microelectrode measurement of membrane potential in VSMCs of intact arteries. Furthermore, T1E3 treatment markedly enhanced the membrane depolarization and contraction of VSMCs in response to several contractile agonists including phenylephrine, endothelin-1, and U-46619. In coimmunoprecipitation experiments, an antibody against BK Ca ␣-subunit [BK Ca (␣)] could pull down TRPC1, and moreover an anti-TRPC1 antibody could reciprocally pull down BK Ca (␣). Double-labeling immunocytochemistry showed that TRPC1 and BK Ca were colocalized in the same subcellular regions, mainly on the plasma membrane, in VSMCs. These data suggest that, TRPC1 physically associates with BK Ca in VSMCs and that Ca 2ϩ influx through TRPC1 activates BK Ca to induce membrane hyperpolarization. The hyperpolarizing effect of TRPC1-BK Ca coupling could serve to reduce agonist-induced membrane depolarization, thereby preventing excessive contraction of VSMCs to contractile agonists. (Circ Res. 2009;104:670-678.)

Ligation of complement receptor 1 increases erythrocyte membrane deformability

“…24 Our results showed that T1E3 recognized an epitope on RBCs ( Figure 2D) and that preincubation of RBCs with T1E3 before CR1 ligation successfully prevented CR1-mediated Ca ϩϩ influx ( Figure 2E). Importantly, sera had to be removed before CR1 ligation by repeated washes to prevent RBC Ca ϩϩ influx followed by RBC lysis due to activation of the classical complement pathway and formation of C5b-9 complex in RBC plasma membrane.…”

Protein Kinase G Inhibits Flow-Induced Ca2+ Entry into Collecting Duct Cells

“…19,20 The specificity of T1E3 was previously confirmed in immunoblots and functional studies. 11,19,20 The immunostaining of nonpermeabilized HEK293 cells that were overexpressed with TRPV4 and TRPC1 showed that T1E3 staining was concentrated at the plasma membrane (Supplemental Figure 2), supporting that T1E3 binds to the extracellular epitope of TRPC1. Interestingly, the T1E3 treatment (1:100 for 1 hour) had no effect on the flow-induced Ca 2+ entry in M1-CCD cells ( Figure 2, C and D).…”

“…19,32 Briefly, a peptide corresponding to the TRPC1 putative pore region (CVGIFCEQQSNDTFHSFIGT) was synthesized and conjugated to a keyhole limpet hemocyanin at Alpha Diagnostic International. The coupled T1E3 peptide was injected to the back of a rabbit followed by two boost doses.…”

Regulation of Cellular Communication by Signaling Microdomains in the Blood Vessel Wall

“…These areas of compartmentalized calcium signaling have also been demonstrated in the systemic circulation, where IP 3 R1, TRPC3, and Cav1 also interact together (Adebiyi et al, 2012). Additionally, another TRP channel can activate BK Ca at the plasma membrane of systemic VSMCs, namely TRPC1, which coimmunoprecipitate and colocalize with BK Ca channels in freshly isolated aortic SMCs (Kwan et al, 2009). Functionally, the authors demonstrated that TRPC1 channels are involved in the responses to several contractile agonists including ET-1, but also phenylephrine and U-46619.…”