FIGURE 1.

Phospholamban regulatome. Scheme of the multimeric protein complex constituted by SERCA2a, PLN, HAX-1, PKA, CAMKII, PP1, Inhibitor-1 (I-1), and Hsp20, which reversibly regulates SR Ca²⁺ transport in the cell. SERCA2a activity is regulated by its reversible inhibitor PLN and the histidine rich Ca²⁺-binding protein (HRC). Phosphorylation of PLN is mediated by cAMP-dependent protein kinase (PKA) at Ser¹⁶ site and Ca²⁺-calmodulin-dependent protein kinase (CaMKII) at Thr¹⁷ site. Dephosphorylation of these sites occurs by protein phosphatase 1 (PP1). The activity of PP1 is regulated by inhibitor-1 (I-1) and Hsp20.