Aquaporin‐1 translocation and degradation mediates the water transportation (1062.2)

Abstract

Acetazolamide (AZA), a prototype of carbonic anhydrase (CA) inhibitor, acts as a diuretic agent with its site of action on renal proximal tubules. These nephron segments also contain aquaporin‐1 (AQP1) water channels, which is required for the formation of concentrated urine. In the present study we examined the role of AQP1 on the diuretic effect of AZA. By using in vivo and in vitro models, we found that the AZA increased the urine volume from 8 hrs to 14 days. However, total CAs activity was decreased within 8 hours and then gradually recovered to the normal level and the CAs protein expression was increased at the beginning of AZA treatment. AQP1 was significantly reduced after AZA administration for 7 days. When combined with NaHCO3, AZA had a more pronounced diuretic effect. But it didn’t induce CA isozymes expression and the CAs activity anymore. However, AQP1 expression was still inhibited from day 7. AZA increased AQP1 ubiquitination in the HK‐2 cell membrane followed by the degradation induced by proteasome. By using the coimmunoprecipitation and the surface plasmon resonance (SPR) methods, we found that AZA facilitated AQP1 translocation onto cell membrane by promoting the interaction of AQP1 and myosin heavy chain (MHC). And this process was mediated by ERK and myosin light chain kinase (MLCK) pathway. These findings indicate that AZA promotes AQP1 translocation and degradation, which may partially mediates the effect of AZA.Grant Funding Source: the National Natural Science Foundation of China (No. 91129727, 81020108031, 30973558)