Expression of ATRAP in adipocytes and negative regulation by beta-adrenergic stimulation of JAK/STAT.

Sympatho-adrenergic activity and the renin-angiotensin system are considered critical regulators of obesity and hypertension. The novel angiotensin II type 1 receptor-associated protein (ATRAP) has been demonstrated to modulate angiotensin II signalling in smooth muscle cells and cardiomyocytes. Adipose tissue expresses important renin angiotensin system components and contributes to cardiometabolic disease. However, ATRAP expression and regulation in adipocytes are unknown. We investigated expression of this novel modulator of angiotensin signalling and its regulation by beta-adrenergic receptors. We found ATRAP to be expressed in differentiated brown and white adipocytes. Stimulation of beta-adrenoceptors strongly suppressed ATRAP expression. We hypothesised a role for JAK/STAT signalling elements. Indeed, beta3-adrenergic stimulation robustly stimulated both STAT1 and STAT3 phosphorylation in a time- and dose-dependent manner. This effect was abrogated by inhibition of PKA and JAK2 signalling. Moreover, inhibition of JAK/STAT and PKA signalling reversed the beta3-adrenergic suppression of ATRAP expression. This study provides the first evidence for expression and adrenergic regulation of the angiotensin II signalling modulator ATRAP in adipocytes. Further, it indicates a novel regulatory link between beta-adrenergic and JAK/STAT signalling.