Myospryn is a calcineurin-interacting protein that negatively modulates slow-fiber-type transformation and skeletal muscle regeneration.

The calcium-calmodulin-regulated protein phosphatase calcineurin plays an important regulatory role in muscle differentiation, fiber-type determination, hypertrophy, and muscle regeneration. Because calcineurin functions in numerous processes in muscle, multiple mechanisms are likely necessary to ensure that the activity of this phosphatase is appropriately regulated. Here we demonstrate that the muscle-specific scaffolding protein myospryn modulates calcineurin signaling by inhibiting calcineurin-dependent transcriptional activity in C2C12 myoblasts through direct interaction with the enzyme via its noncanonical tripartite motif (TRIM-like).

Modulation of angiotensin II-mediated cardiac remodeling by the MEF2A target gene Xirp2.

Rationale: The vasoactive peptide angiotensin II (Ang II) is a potent cardiotoxic hormone whose actions have been well studied, yet questions remain pertaining to the downstream factors that mediate its effects in cardiomyocytes.

Objective: The in vivo role of the myocyte enhancer factor (MEF)2A target gene Xirp2 in Ang II-mediated cardiac remodeling was investigated.

Methods And Results: Here we demonstrate that the MEF2A target gene Xirp2 (also known as cardiomyopathy associated gene 3 [CMYA3]) is an important effector of the Ang II signaling pathway in the heart.