VACM-1/cul5 Expression in Vascular Tissue in Vivo is Induced by Water Deprivation and its Expression in Vitro Regulates Aquaporin-1 Concentrations
VACM-1, a cul5 gene product, when overexpressed in vitro, has an antiproliferative effect. In vivo, VACM-1/cul5 is present in tissues involved in the regulation of water balance. Neither proteins targeted for VACM-1/cul5-specific degradation nor factors that may regulate its expression in those tissues have been studied. To identify genes that may be misregulated by VACM-1 cDNA, we performed microarray analysis. Our results indicate that in cos-1 cells transfected with VACM-1 cDNA, mRNA levels for several genes, including AQP1, were decreased when compared to the control group. Our results also indicate that in cos-1 cells transfected with VACM-1 cDNA, endogenous AQP1 protein was decreased about 6-fold when compared to the controls. To test the hypothesis that VACM-1/cul5 may be regulated by conditions that compromise water homeostasis in vivo, we determined if 24 h of water deprivation affects VACM-1/cul5 levels or the effect of VACM-1/cul5 on AQP1. VACM-1 mRNA and protein levels were significantly higher in rat mesenteric arteries, skeletal muscle and the heart ventricle but not in the heart atrium from 24-h water-deprived rats when compared to the controls. Interestingly, 24 h of water deprivation increased modification of VACM-1 by an ubiquitin-like protein, Nedd8, essential for cullin-dependent E3 ligase activity. Although water deprivation did not significantly change AQP1 levels in the mesenteric arteries, AQP1 protein concentrations were inversely correlated with the ratio of the VACM-1 to Nedd8-modified VACM-1. These results suggest that VACM-1/cul5 may regulate endothelial AQP1 concentration both in vivo and in vitro.
Johnson, Alyssa E., Isabelle P. Le, Bradley T. Andresen, Joseph Stodola, Gary L. Dewey, Shirley B. Dean, James Resau, Pete Haak, Travis Ruch, Ashleigh Sartor, Inara Lazdins, Christopher C. Barney and Maria Burnatowska Hledin. "Vacm-1/Cul5 Expression in Vascular Tissue in Vivo Is Induced by Water Deprivation and Its Expression in Vitro Regulates Aquaporin-1 Concentrations." Cell and Tissue Research 349, no. 2 (2012): 527-39.