Anti-OSR1 (aa 1-100) polyclonal antibody

SPAK [STE20 (sterile 20)/SPS1-related proline/alanine-rich kinase] kinase consists of a full-length (FL-) and an alternatively spliced kidney-specific (KS-) isoform. SPAK regulates the NaCl cotransporter (NCC) in the distal convoluted tubule (DCT). The relative abundance and role of FL-vs. KS-SPAK in regulating Na+ -K+ -2Cl(-) cotransporter (NKCC2) in thick ascending limb (TAL) are not completely understood. Here, we report that FL-SPAK mRNA was the most abundant in medullary TAL (mTAL), followed by cortical TAL (cTAL) and DCT. KS-SPAK mRNA abundance was relatively lower than FL-SPAK. The ratios of FL-SPAK to KS-SPAK in mTAL, cTAL, and DCT were 12.3, 12.5, and 10.2, respectively. To examine the role of SPAK in the regulation of sodium transport in TAL, we used in vitro microperfusion of mTAL and cTAL isolated from wild-type (WT) and SPAK knockout mice (SPAK-KO) that lack both FL-and KS-SPAK. The rates of sodium absorption in cTAL and mTAL of SPAK-KO mice were 34.5 and 12.5% of WT tubules, respectively. The mRNA levels of related OSR1 kinase and SPAK protease Dnpep in SPAK-KO tubules were not significantly different from WT tubules. We next examined the role of SPAK in the regulation of sodium reabsorption by vasopressin in TAL. Vasopressin increased sodium reabsorption by similar to 80% in both mTAL and cTAL from WT mice. While baseline sodium reabsorption was lower in SPAK-KO tubules, vasopressin increased sodium reabsorption over twofold. In conclusion, the combined net effect of SPAK isoforms on sodium reabsorption in TAL is stimulatory. SPAK is not essential for vasopressin stimulation of sodium reabsorption in TAL.

Receptor Expressed in Lymphoid Tissues (RELT) is a human Tumor Necrosis Factor Receptor (TNFR) family member that has two identified homologous binding partners, RELL1 and RELL2. This study sought to further understand the pattern of RELT expression, the functional role of RELT family members, and the mechanism of RELT-induced apoptosis. RELT protein expression was detected in the spleen, lymph node, brain, breast and peripheral blood leukocytes (PBLs). A smaller than expected size of RELT was observed in PBLs, suggesting a proteolytically cleaved form of RELT. RELL1 and RELL2 overexpression activated the p38 MAPK pathway more substantially than RELT in HEK-293 cells, and this activation of p38 by RELT family members was blocked by dominant-negative mutant forms of OSR1 or TRAF2, implicating these molecules in RELT family member signaling. RELT was previously shown to induce apoptosis in human epithelial cells despite lacking the characteristic death domain (DD) found in other TNFRs. Seven deletion mutants of RELT that lacked differing portions of the intracellular domain were created to assess whether RELT possesses a novel DD. None of the deletion mutants induced apoptosis as efficiently as full-length RELT, a result that is consistent with a novel DD being located at the carboxyl terminus. Interestingly, induction of apoptotic morphology by RELT overexpression was not prevented when signaling by FADD or Caspase-8 was blocked, indicating RELT induces apoptosis by a pathway distinct from other death-inducing TNFRs such as TNFR1. Collectively, this study provides more insights into RELT expression, RELT family member function, and the mechanism of RELT-induced death. (C) 2017 Elsevier Inc. All rights reserved.