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1 Physiology, Biophysics and Medicine, University of Southern California, Los Angeles, California, United States
2 Institute of Genetics, University of Bonn, Bonn, Germany
3 Institute of Genetics, Division of Molecular Genetics, University of Bonn, Bonn, Germany
4 Physiology, University of Southern California, Los Angeles, California, United States
5 Institut fuer Genetik Uni Bonn, Bonn, Germany; Institute of Genetics, Division of Molecular Genetics, University of Bonn, Bonn, Germany
6 Dept. of Physiology & Biophysics, Univ. Southern California, Los Angeles, California, United States
* To whom correspondence should be addressed. E-mail: petipete{at}usc.edu.
Connexin (Cx) proteins are known to play a role in cell to cell communication via intercellular gap junction channels or transiently open hemichannels. Previous studies have identified several connexin isoforms in the juxtaglomerular apparatus (JGA), but the vascular connexin isoform Cx45 has not yet been studied in this region. The present work aimed to identify in detail the localization of Cx45 in the JGA and to suggest a functional role for Cx45 in the kidney using conditions where Cx45 expression or function was altered. Using mice expressing LacZ coding DNA under the control of the Cx45 promoter, we observed 
-galactosidase staining in cortical vasculature and glomeruli, with specific localization to the JGA region. Renal vascular localization of Cx45 was further confirmed using conditional Cx45-deficient (Cx45fl/fl:Nestin-Cre) mice which express EGFP instead of Cx45 in cells that during development expressed the intermediate filament nestin. EGFP fluorescence was found in the afferent and efferent arteriole smooth muscle cells, renin producing JG cells and in the extra- and intraglomerular mesangium. Cx45fl/fl:Nestin-Cre mice exhibited increased renin expression and activity, as well as higher systemic blood pressure. The propagation of mechanically-induced calcium waves was slower in cultured vascular smooth muscle cells (VSMCs) from Cx45fl/fl:Nestin-Cre mice as well as in control VSMC treated with a Cx45 blocker. In conclusion, the localization of Cx45 to the JGA and functional data from Cx45fl/fl:Nestin-Cre mice suggest that Cx45 is involved in the propagation of JGA vascular signals and in the regulation of renin release and blood pressure.
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