title: Ca(2+) is a Regulator of the WNK/OSR1/NKCC Pathway in a Human Salivary Gland Cell Line.
abstract: Wnk kinase maintains cell volume, regulating various transporters such as sodium-chloride cotransporter, potassium-chloride cotransporter, and sodium-potassium-chloride cotransporter 1 (NKCC1) through the phosphorylation of oxidative stress responsive kinase 1 (OSR1) and STE20/SPS1-related proline/alanine-rich kinase (SPAK). However, the activating mechanism of Wnk kinase in specific tissues and specific conditions is broadly unclear. In the present study, we used a human salivary gland (HSG) cell line as a model and showed that Ca(2+) may have a role in regulating Wnk kinase in the HSG cell line. Through this study, we found that the HSG cell line expressed molecules participating in the WNK-OSR1-NKCC pathway, such as Wnk1, Wnk4, OSR1, SPAK, and NKCC1. The HSG cell line showed an intracellular Ca(2+) concentration ([Ca(2+)]i) increase in response to hypotonic stimulation, and the response was synchronized with the phosphorylation of OSR1. Interestingly, when we inhibited the hypotonically induced [Ca(2+)]i increase with nonspecific Ca(2+) channel blockers such as 2-aminoethoxydiphenyl borate, gadolinium, and lanthanum, the phosphorylated OSR1 level was also diminished. Moreover, a cyclopiazonic acid-induced passive [Ca(2+)]i elevation was evoked by the phosphorylation of OSR1, and the amount of phosphorylated OSR1 decreased when the cells were treated with BAPTA, a Ca(2+) chelator. Finally, through that process, NKCC1 activity also decreased to maintain the cell volume in the HSG cell line. These results indicate that Ca(2+) may regulate the WNK-OSR1 pathway and NKCC1 activity in the HSG cell line. This is the first demonstration that indicates upstream Ca(2+) regulation of the WNK-OSR1 pathway in intact cells.
authors.affiliation: Department of Oral Biology, BK21 PLUS Project, Yonsei University College of Dentistry, Seoul 120-752, Korea.
authors.forename: Soonhong
authors.initials: S
authors.lastname: Park
authors.affiliation: Department of Oral Medicine, Yonsei University College of Dentistry, Seoul 120-752, Korea.
authors.forename: Sang Kyun
authors.initials: SK
authors.lastname: Ku
authors.affiliation: Department of Oral Biology, BK21 PLUS Project, Yonsei University College of Dentistry, Seoul 120-752, Korea.
authors.forename: Hye Won
authors.initials: HW
authors.lastname: Ji
authors.affiliation: Department of Oral Medicine, Yonsei University College of Dentistry, Seoul 120-752, Korea.
authors.forename: Jong-Hoon
authors.initials: JH
authors.lastname: Choi
authors.affiliation: Department of Oral Biology, BK21 PLUS Project, Yonsei University College of Dentistry, Seoul 120-752, Korea.
authors.forename: Dong Min
authors.initials: DM
authors.lastname: Shin
keywords: Ca2+ signaling; NKCC; OSR1; Salivary gland; WNK