Phospholamban (PLN) is a mini-membrane protein that directly controls the cardiac Ca2+-transport response to β-adrenergic stimulation, thus modulating cardiac output during the fight-or-flight response. In the sarcoplasmic reticulum membrane, PLN binds to the sarco(endo) plasmic reticulum Ca2+-ATPase (SERCA), keeping this enzyme’s function within a narrow physiological window. PLN phosphorylation by cAMP-dependent protein kinase A or increase in Ca2+ concentration reverses the inhibitory effects through an unknown mechanism. Using oriented- sample solid-state NMR spectroscopy and replica-averaged NMR-restrained structural refinement, we reveal that phosphorylation of PLN’s cytoplasmic regulatory domain signals the disruption of several inhibitory contacts at the transmembrane binding interface of the SERCA-PLN complex that are propagated to the enzyme’s active site, augmenting Ca2+ transport. Our findings address long- standing questions about SERCA regulation, epitomizing a signal transduction mechanism operated by posttranslationally modified bitopic membrane proteins.
Bibliographical noteFunding Information:
This work was supported by the National Institute of Health grants R01 GM064742 and R01 HL144100 to GV and R01HL139065 and R37AG026160 to DDT and RLC; and European Research Council (CoG - BioDisOrder - 819644) funding to ADS DW was supported by an American Heart Association Postdoctoral Fellowship (19POST34420009). The authors thank Dr. Sanz-Hernández for his initial contribution to the project.
© Weber et al.