Emerging role of Akt substrate protein AS 160 in the regulation of AQP2 translocation

Hyo Young Kim, Hyo Jung Choi, Jung Suk Lim, Eui Jung Park, Hyun Jun Jung, Yu Jung Lee, Sang Yeob Kim, Tae Hwan Kwon

Research output: Contribution to journalArticle

Abstract

AS160, a novel Akt substrate of 160 kDa, contains a Rab GTP aseactivating protein (GAP) domain. The present study examined the role of Akt and AS160 in aquaporin-2 (AQP2) trafficking. The main strategy was to examine the changes in AQP2 translocation in response to small interfering RNA (siRNA)-mediated AS160 knock down in mouse cortical collecting duct cells (M-1 cells and mpkCCDc14 cells).Short-term dDAVP treatment in M-1 cells stimulated phosphorylation of Akt (S473) and AS160, which was also seen in mpkCCDc14 cells. Conversely, the phosphoinositide 3-kinase (PI3K) inhibitor LY294002 diminished phosphorylation of Akt (S473) and AS160. Moreover, siRNA-mediated Akt1 knockdown was associated with unchanged total AS160 but decreased phospho-AS160 expression, indicating that phosphorylation of AS160 is dependent on PI3K/Aktpathways. siRNA-mediated AS160 knockdown significantly decreased total AS160 and phospho-AS160 expression. Immunocy to chemistry revealed that AS160 knockdown in mpkCCDc14 cells was associated with increased AQP2 density in the plasma membrane [135±3%of control mpkCCDc14 cells (n = 65), P < 0.05, n = 64] despite the absence of dDAVP stimulation. Moreover, cell surface biotinylationas says of mpkCCDc14 cells with AS160 knockdown exhibited significantly higher AQP2 expression [150 ± 15% of controlmpkCCDc14 cells (n = 3), P < 0.05, n = 3]. Taken together, PI3K/Akt pathways mediate the dDAVP-induced AS160 phosphorylation, and AS160 knockdown is associated with higherAQP2 expression in the plasma membrane. Since AS160 contains a GAP domain leading to a decrease in the active GTP-bound form of AS160 target Rab proteins for vesicle trafficking, decreased expression of AS160 is likely to play a role in the translocation ofAQP2 to the plasma membrane

Original languageEnglish (US)
Pages (from-to)F151-F161
JournalAmerican Journal of Physiology - Renal Physiology
Volume301
Issue number1
DOIs
StatePublished - Jul 1 2011
Externally publishedYes

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Keywords

  • Aquaporin
  • Collecting duct
  • Rab gtpase-activating protein
  • Vasopressin

ASJC Scopus subject areas

  • Physiology
  • Urology

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