This family consists of several mammalian calcineurin-binding proteins. The calcium- and calmodulin-dependent protein phosphatase calcineurin has been implicated in the transduction of signals that control the hypertrophy of cardiac muscle and slow fibre gene expression in skeletal muscle. Calsarcin-1 and calsarcin-2 are expressed in developing cardiac and skeletal muscle during embryogenesis, but calsarcin-1 is expressed specifically in adult cardiac and slow-twitch skeletal muscle, whereas calsarcin-2 is restricted to fast skeletal muscle. Calsarcins represent a novel family of sarcomeric proteins that link calcineurin with the contractile apparatus, thereby potentially coupling muscle activity to calcineurin activation [1]. Calsarcin-3, is expressed specifically in skeletal muscle and is enriched in fast-twitch muscle fibres. Like calsarcin-1 and calsarcin-2, calsarcin-3 interacts with calcineurin, and the Z-disc proteins alpha-actinin, gamma-filamin, and telethonin [2].

1: Calsarcins, a novel family of sarcomeric calcineurin-binding proteins. Frey N, Richardson JA, Olson EN; Proc Natl Acad Sci U S A 2000;97:14632-14637. PMID:11114196

2: Calsarcin-3, a novel skeletal muscle-specific member of the calsarcin family, interacts with multiple Z-disc proteins. Frey N, Olson EN; J Biol Chem 2002;277:13998-14004. PMID:11842093