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. Author manuscript; available in PMC: 2013 May 1.
Published in final edited form as: Trends Endocrinol Metab. 2012 Apr 18;23(5):216–222. doi: 10.1016/j.tem.2012.03.003

Figure 3. Schematic representation of open hypotheses for alpha and beta arrestin actions on beta-adrenergic receptors in adipose tissue.

Figure 3

A) Activation of the adipose tissue β1 and β2 adrenergic receptors causes a Gs-mediated increase in cAMP levels, stimulating lipolysis. This receptor has a classical paradigm for desensitization in which beta-arrestins are recruited to the active phosphorylated receptor, leading to ubiquitination and clathrin-mediated endocytosis [11]. We hypothesize that alpha-arrestins such as Arrdc3 may serve similar roles in this process. B) In contrast, the β3-adrenergic receptor is not phosphorylated and is largely not downregulated, at least in vitro. Furthermore, signaling is through Gi activation of ERK and through G-protein-independent recruitment of Src [63]. Whereas beta-arrestins are not recruited to the β3-adrenergic receptor, we hypothesize that alpha-arrestins may be able to either promote receptor ubiquitination or alter downstream signaling, thereby regulating thermogenesis in adipose tissue.