Beta-1 adrenergic receptor, Beta-2 adrenergic receptor and Beta-3 adrenergic receptor are activated by Epinephrine and L-Noradrenaline. Conventional signaling is accomplished via G-protein alpha-s/ Adenylate cyclase that leads to Cyclic AMP production and activation of PKA-reg (cAMP-dependent) and PKA-cat (cAMP-dependent) [1]. AKAP6 is an anchor protein that enables PKA-cat (cAMP-dependent) phosphorylation [2], [3]. Beta-2 adrenergic receptor signaling appears to be localized to plasma membrane, unlike that of Beta-1 adrenergic receptor [4].

Beta-1 adrenergic receptor coupled PKA-cat (cAMP-dependent) phosphorylates Phospholamban. Phosphorylation of Phospholamban is believed to release its tonic inhibition of Ca-ATPase1 and (Ca-ATPase2 and to Ca('2+) flux to endoplasmatic reticulum. Ca('2+) flux from cytoplasm accelerates relaxation of cardiac muscle [5].

Also PKA-cat (cAMP-dependent) phosphorylates Troponin I, cardiac. Phosphorylation prevents Troponin I, cardiac interaction with Troponin C, cardiac and leads to weaker Ca('2+) binding and thereby to relaxation of cardiac muscle [5], [6]. PKA-cat (cAMP-dependent)-mediated phosphorylation of Troponin I, cardiac is antagonized by dephosphorylation by PP2A catalytic [7].

PKA-cat (cAMP-dependent) phosphorylation of Ryanodine receptor 2 leads to elevated Ca('2+) flux to cytoplasm. Elevated Ca('2+) in cardiac muscles normally has chronotropic effect [3], [5].

PKA-cat (cAMP-dependent), e.g., in cardiomyocytes, activates PHK alpha (muscle) and PHK gamma (muscle)/ PYGM and this leads to acceleration of glycogen breakdown rate [5], [6].

Activated by Beta-1 adrenergic receptor and Beta-2 adrenergic receptor, PKA-cat (cAMP-dependent) participates in activation of L-type Ca(II) channel, alpha 1C subunit. Ca('2+) current via (L-type Ca(II) channel, alpha 1C subunits elevates Ca('2+) levels in cytosol. This process leads to contraction of cardiomyocytes [4], [8]. Elevated level of Ca('2+) in cardiomyocytes leads to activation of Calmodulin/ CaMK II. CaMK II phospholylates L-type Ca(II) channel, alpha 1C subunit and Phospholamban [5]. PKA-cat (cAMP-dependent)-mediated activation of PDE4D and PDE3A leads to decrease in Cyclic AMP level in cytoplasm due to conversion of Cyclic AMP to AMP by PDE [5], [9], [10].

PKA-cat (cAMP-dependent) activated by Beta-2 adrenergic receptor and Beta-3 adrenergic receptor presumably phosphorylates BETA-PIX [11] which in turn activates CDC42/ MEKK4(MAP3K4)/ MEK6(MAP2K6) and MEK3(MAP2K3)/ p38 MAPK [12], [13], leading to relaxation relaxation of cardiac muscle [12]. In white/brown adipocytes and intestinal smooth muscle cells, the above ivents lead to activation of PPARGC1 (PGC1-alpha)/ PPAR-gamma. PPAR-gamma is in a complex with PPAR-gamma/RXR-alpha that participates in transcriptional activation of UCP1. UCP1 participates in physiological processes of nonshivering thermogenesis in brown adipocites and in relaxation of intestinal smooth muscle cells [13], [14].

PKA-cat (cAMP-dependent) activated by Beta-3 adrenergic receptor phosphorylates Lipase hormone-sensitive (LIPS) and Perilipin, the latter being a facilitator of LIPS activity. This way, Beta-3 adrenergic receptor stimulates lipolysis (see lipid catabolic process) [15].

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