Abstract
The Popeye domain containing (POPDC) genes encode a novel class of cAMP effector proteins, which are abundantly expressed in heart and skeletal muscle. Here, we will review their role in striated muscle as deduced from work in cell and animal models and the recent analysis of patients carrying a missense mutation in POPDC1. Evidence suggests that POPDC proteins control membrane trafficking of interacting proteins. Furthermore, we will discuss the current catalogue of established protein-protein interactions. In recent years, the number of POPDC-interacting proteins has been rising and currently includes ion channels (TREK-1), sarcolemma-associated proteins serving functions in mechanical stability (dystrophin), compartmentalization (caveolin 3), scaffolding (ZO-1), trafficking (NDRG4, VAMP2/3) and repair (dysferlin) or acting as a guanine nucleotide exchange factor for Rho-family GTPases (GEFT). Recent evidence suggests that POPDC proteins might also control the cellular level of the nuclear proto-oncoprotein c-Myc. These data suggest that this family of cAMP-binding proteins probably serves multiple roles in striated muscle.
Highlights
The Popeye domain containing genes encode a class of 31-51-cyclic adenosine monophosphate effector proteins, which is abundantly expressed in cardiac and skeletal muscle [1]
Three well-characterized classes of cyclic adenosine monophosphate (cAMP) effector proteins are known: protein kinase A (PKA), exchange factor directly activated by cAMP (EPAC) and the cyclic nucleotide-gated ion channels (CNGC) [6]
The cyclic nucleotide receptor involved in sperm function (CRIS) has been identified as the fourth cAMP effector protein and plays a role in sperm maturation and motility [7]
Summary
The Popeye domain containing genes encode a class of 31-51-cyclic adenosine monophosphate (cAMP) effector proteins, which is abundantly expressed in cardiac and skeletal muscle [1]. An intricate network of cAMP-producing enzymes (adenylate cyclases), effector proteins, cAMP-degrading enzymes (phosphodiesterases), as well as scaffolding proteins (e.g., AKAPs) are present in eukaryotic cells [4]. This protein network ensures that the production of cAMP is compartmentalized, allowing the activation of cAMP effector proteins and their downstream targets in a spatio-temporally-controlled manner [5]. The Popeye domain containing (POPDC) genes encode a fifth class of cAMP-effector proteins, which displays a prominent expression in striated muscle tissue [8]. We will discuss some recent evidence suggesting an important role of POPDC proteins in the control of cell proliferation and wound healing
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