Proceedings of The Physiological Society
University of Oxford (2011) Proc Physiol Soc 23, PC307
Functional regulation of transient receptor potential vanilloid type(TRPV) 6 channel by extracellular pH
B. I. Yeh1, K. H. Lee2, S. W. An3
1. Biochemistry, Yonsei University, Wonju College of Medicine, Wonju, Gangwondo, Korea, Republic of. 2. Anesthesiology, Yonsei University, Wonju College of Medicine, Wonju, Gangwondo, Korea, Republic of. 3. Pharmacology, Yonsei University, Wonju College of Medicine, Wonju, Gangwondo, Korea, Republic of.
The major role of TRPV6 has been known to absorb calcium in small intestine from the food. The amino acid sequences of TRPV6 have 30% homology with TRPV5, but the homology in pore helix is about 75% and their structures in pore helix are very similar. The extracellular pH sensitivity of TRPV5 have studied already, but TRPV6 has not done yet. Maybe this is because the organs where TRPV6 distributes are generally insensitive to extracellular pH, and therefore, it’s difficult to determine physiological meaning of extracellular pH sensitivity of TRPV6. As it is known that calcium is very important for wound healing and aging in skin, there is a possibility TRPV6 play an important role in the calcium concentration regulation in epidermis. It is known that epidermal and dermal pHs are different each other and their calcium concentrations are easily variable. Therefore, this study was planned to check extracellular pH sensitivities of TRPV6 which is related with wound healing and/or skin aging. For this, extracellular pH sensitivity of TRPV6 was examined using whole-cell patch clamp technique in CHO(chinese hamster ovary) cells. The pKa, 50% of currents are inhibited from the maximum, was 5.71±0.27. The 521st histidine was insensitive to extracellular pH changes, so it may play as an extracelluar pH sensor. To explain the mechanism how proton affects the function of TRPV6 substituted cysteine accessibility method(SCAM) was performed. The currents of 521st histidine to cysteine mutant was inhibited by MTSET and the mechanism for such a phenomenon is possibly due to conformational changes. In conclusion, the 521st histidine plays a role as extracellular pH sensor and it causes the functional declines not by direct blocking effect or electrostatic effect but by conformational changes through proton binding.
Where applicable, experiments conform with Society ethical requirements