Meeting Abstract
P2.154 Monday, Jan. 5 Phosphorylation state of Na-K-Cl cotransporter in the intestine of euryhaline teleosts in response to varying osmolality MONETTE , Michelle Y.*; FORBUSH, Biff; Yale School of Medicine and Mt. Desert Island Biological Laboratory; Yale School of Medicine and Mt. Desert Island Biological Laboratory michellemonette@yale.edu
The Na-K-Cl cotransporter (NKCC) couples the movement of Na, K, and Cl across polarized cell membranes. Two NKCC isoforms have been cloned: NKCC1, a ubiquitously expressed secretory isoform with an important role in the regulation of intracellular Cl and cell volume, and NKCC2, a kidney-specific absorptive isoform expressed in the thick ascending limb of the loop of Henle. In teleosts, NKCC2 is present in the apical membrane of the intestine where it functions in osmo- and iono- regulation. Estuarine teleosts, experience rapid salinity changes and must be able to regulate plasma ion concentrations. To cope with hyperosmotic stress, teleosts drink seawater, absorb Na and Cl via apical NKCC2 in the intestine, and secrete excess ions via the gill. It is hypothesized that rapid activation of NKCC2 is achieved in part by protein phosphorylation, as has been demonstrated for NKCC1. This study examined the in vitro and in vivo phosphorylation state of NKCC in the intestine of killifish and flounder in response to varying osmolality using immunological techniques and detection with NKCC antibodies, R5 (phospho-specific) and T4. Phosphorylated NKCC was highly expressed in the intestine of killifish and flounder. Exposure of killifish and flounder intestine to high osmolality in vitro resulted in a reduction in R5 signal, whereas no effect on T4 signal was observed. Loss in R5 signal after incubation in high osmolality was almost fully reversible after a subsequent incubation in low osmolality. These data demonstrate changes in the phosphorylation state of NKCC in the intestine of euryhaline teleosts upon exposure to varying osmolality, supporting the hypothesis that phosphorylation plays a role in regulating NKCC during acute salinity changes.
