Renal Expression of Collectrin (TMEM27) is Downregulated During Angiotensin II-induced Hypertension

Collectrin (Tmem27) is transmembrane glycoprotein with homology to ACE-2, but lacks any catalytic domain. It plays a key role as a chaperone of amino acid transporters, and is abundantly expressed in the kidney in the proximal tubules and collecting duct. Deletion of collectrin in the mouse results in hypertension (HTN) at baseline and augmented salt-sensitivity that are associated with decreased renal nitric oxide and increased superoxide levels. During high salt diet, renal expression of collectrin is upregulated, suggesting an adaptive homeostatic response to salt loading. Here, we queried whether the expression of collectrin is regulated by angiotensin II (Ang II). Wild-type 129S6 mice were made hypertensive with Ang II osmotic minipump @ 600 ng/kg/min x 2 weeks, and were compared to age-matched untreated WT 129 mice. Shown in Fig. 1, renal mRNA expression of collectrin is significantly reduced after 2 weeks of Ang II (Panel A). Immunostaining shows collectrin protein level is also significantly diminished to near undetectable level (Panel B). We show for the first time that Ang II regulates the expression of collectrin, suggesting that the action of Ang II on blood pressure may be mediated, in part, through the downregulation of collectrin. Further studies are needed to determine the effect of AT1 and AT2 receptor signaling on renal expression of collectrin during Ang II-HTN in vivo.