Connexin45 is expressed in the juxtaglomerular apparatus and is involved in the regulation of renin secretion and blood pressure.
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 that express lacZ coding DNA under the control of the Cx45 promoter, we observed beta-galactosidase staining in cortical vasculature and glomeruli, with specific localization to the JGA region. Renal vascular localization of Cx45 was further confirmed with the use of conditional Cx45-deficient (Cx45fl/fl:Nestin-Cre) mice, which express enhanced green fluorescence protein (EGFP) instead of Cx45 only in cells that, during development, expressed the intermediate filament nestin. EGFP fluorescence was found in the afferent and efferent arteriole smooth muscle cells, in the renin-producing juxtaglomerular 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 and in control VSMC treated with a Cx45 gap mimetic peptide that inhibits Cx45 gap junctional communication. VSMCs allowed the cell-to-cell passage of the gap junction permeable dye Lucifer yellow, and calcium wave propagation was not altered by addition of the ATP receptor blocker suramin, suggesting that Cx45 regulates calcium wave propagation via direct gap junction coupling. 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.
Hanner
Fiona
F
Department of Physiology, Zilkha Neurogenetic Institute, University of Southern California, 1501 San Pablo St., ZNI 335, Los Angeles, CA 90033, USA.
von Maltzahn
Julia
J
Maxeiner
Stephan
S
Toma
Ildiko
I
Sipos
Arnold
A
Krüger
Olaf
O
Willecke
Klaus
K
Peti-Peterdi
János
J
D000818:Animals; D001160:Arterioles / Q000378:metabolism; D001794:Blood Pressure; D020013:Calcium Signaling; D002478:Cells, Cultured; D017630:Connexins / Q000235:genetics / Q000378:metabolism*; D017629:Gap Junctions / Q000378:metabolism; D017930:Genes, Reporter; D049452:Green Fluorescent Proteins / Q000235:genetics; D007381:Intermediate Filament Proteins / Q000235:genetics; D007606:Juxtaglomerular Apparatus / Q000098:blood supply / Q000187:drug effects / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D009131:Muscle, Smooth, Vascular / Q000378:metabolism; D009419:Nerve Tissue Proteins / Q000235:genetics; D064231:Nestin; D011401:Promoter Regions, Genetic; D058919:Purinergic P2 Receptor Antagonists; D012083:Renin / Q000378:metabolism*; D013498:Suramin / Q000494:pharmacology; D001616:beta-Galactosidase / Q000235:genetics
D017630:Connexins; D007381:Intermediate Filament Proteins; D009419:Nerve Tissue Proteins; C577485:Nes protein, mouse; D064231:Nestin; D058919:Purinergic P2 Receptor Antagonists; C082920:connexin 45; C485184:enhanced green fluorescent protein; D049452:Green Fluorescent Proteins; D013498:Suramin; D001616:beta-Galactosidase; D012083:Renin