TY - JOUR
T1 - STE20/SPS1-related proline/alanine-rich kinase (SPAK) is critical for sodium reabsorption in isolated, perfused thick ascending limb
AU - Cheng, Chih Jen
AU - Yoon, Joonho
AU - Baum, Michel
AU - Huang, Chou Long
N1 - Publisher Copyright:
© 2015 the American Physiological Society.
PY - 2015
Y1 - 2015
N2 - 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 ∼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.
AB - 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 ∼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.
KW - SPAK
KW - Sodium
KW - Thick ascending limb
KW - Vasopressin
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U2 - 10.1152/ajprenal.00493.2013
DO - 10.1152/ajprenal.00493.2013
M3 - Article
C2 - 25477470
AN - SCOPUS:84924083221
SN - 1931-857X
VL - 308
SP - F437-F443
JO - American Journal of Physiology - Renal Physiology
JF - American Journal of Physiology - Renal Physiology
IS - 5
ER -