Phospholemman (PLM) is a 72-amino-acid type I single-span membrane protein, belonging to the FXYD (pronounced “fix-it”) family of ion transport regulators. These smallmembrane proteins are tissue-specific regulators of the Na/K ATPase (Na/K pump or NKA). PLM is predominantly expressed in striated (cardiac and skeletal) and smooth muscle (Bogaev et al. 2001; Rembold et al. 2005). However, it is also detectable to a lesser extent in the kidney (Wetzel and Sweadner 2003), liver (Bogaev et al. 2001), cerebellum, and choroid plexus (Feschenko et al. 2003).
PLM was first identified in canine and guinea pig myocardium as a 15 kDa sarcolemmal protein and was later shown to be the principle sarcolemmal substrate for protein kinases A and C (PKA and PKC) (Presti et al. 1985a, b). At the time, the correlation between PLM phosphorylation and PKA-induced positive inotropy led Prest and colleagues to speculate that this...
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