Question: Is phospholamban phosphorylated by Protein kinase A?

Context:
cAMP-dependent protein kinase (PKA) phosphorylation of PLB
phosphorylation of PLN, at either Ser(16) by PKA 
Activation of cardiac muscle sarcoplasmic reticulum Ca2+-ATPase (SERCA2a) by beta1-agonists involves cAMP- and PKA-dependent phosphorylation of phospholamban (PLB), which relieves the inhibitory effects of PLB on SERCA2a. 
Phospholamban (PLB) is a sarcoplasmic reticulum (SR) protein that when phosphorylated at Ser16 by PKA
phosphorylation of PLB by the Ca2+-calmodulin-dependent protein kinase (CaMK) and cAMP-dependent protein kinase (PKA). 
cAMP-dependent protein kinase (PKA)-mediated phospholamban (PLB) phosphorylation at serine-16
Phospholamban (PLB) is a major target of the beta-adrenergic cascade in the heart, functioning to modulate contractile force by altering the rate of calcium re-sequestration by the Ca-ATPase. Functionally, inhibition by PLB binding is manifested by shifts in the calcium dependence of Ca-ATPase activation toward higher calcium levels; phosphorylation of PLB by PKA reverses the inhibitory action of PLB.
phosphorylation of both PLB residues (Ser16, PKA site, and Thr17, CaMKII site) 
Phosphorylation of Ser(16) by PKA
stabilization of the structure of PLB following phosphorylation of Ser(16)
Phospholamban (PLB) inhibits the sarcoplasmic reticulum (SR) Ca(2+)-ATPase, and this inhibition is relieved by cAMP-dependent protein kinase (PKA)-mediated phosphorylation. 
Two-dimensional tryptic peptide maps of phosphorylated phospholamban indicated that cAMP-dependent protein kinase phosphorylates at a single site, A, and Ca2+-calmodulin-dependent protein kinase phosphorylates at sites C1 and C2 in the low molecular weight form, where A is different from C1 but may be the same as C2.
Because SR function is regulated by phosphorylation of phospholamban (PLB), a SR protein phosphorylated by cAMP-dependent protein kinase (PKA) at Ser(16)and Ca(2+)-calmodulin-dependent protein kinase (CaMKII) at Thr(17), the phosphorylation of these residues during ischemia and reperfusion was examined in Langendorff-perfused rat hearts
These changes were associated with reduced protein expression of sarcoplasmic reticulum Ca(2+)-ATPase (SERCA2a) and protein kinase A phosphorylated phospholamban (PLB), which was reduced in HF, but essentially abolished in VD-HF
The data indicate that 1) phosphorylation of phospholamban at Ser16 by cAMP-dependent protein kinase is the main regulator of beta-adrenergic-induced cardiac relaxation definitely preceding Thr17 phosphorylation and 2) the beta-adrenergic-mediated phosphorylation of Thr17 by Ca2+-calmodulin-dependent protein kinase required influx of Ca2+ through the L-type Ca2+ channel
Here we extend this model to explain the reversal of SERCA2a inhibition that occurs after phosphorylation of PLB at Ser(16) by protein kinase A (PKA) and after binding of the anti-PLB monoclonal antibody 2D12, which recognizes residues 7-13 of PLB
Phospholamban is phosphorylated in heart by cAMP-dependent protein kinase, cGMP-dependent protein kinase and calcium/calmodulin-dependent protein kinase II (CM-kinase-II) and in smooth muscle cells by cGMP-dependent protein kinase
Phospholamban, the cardiac sarcoplasmic reticulum proteolipid, is phosphorylated by cAMP-dependent protein kinase, by Ca2+/phospholipid-dependent protein kinase, and by an endogenous Ca2+/calmodulin-dependent protein kinase, the identity of which remains to be defined

Answer: Phospholamban (PLB) is a sarcoplasmic reticulum (SR) protein that is phosphorylated at Ser16 by PKA. Phosphorylation of PLB by PKA reverses the inhibitory action of PLB.
Exact answer: yes