ANKRD2

Ankyrin Repeat, PEST sequence and Proline-rich region (ARPP), also known as Ankyrin repeat domain-containing protein 2, is a protein that in humans is encoded by the ANKRD2 gene. ARPP is a member of the muscle ankyrin repeat proteins (MARP), which also includes CARP and DARP, and is highly expressed in cardiac and skeletal muscle and in other tissues. Expression of ARPP has been shown to be altered in patients with dilated cardiomyopathy and amyotrophic lateral sclerosis. A role for Ankrd2 in tumor progression and metastases spreading has also been described.

Ankyrin Repeat, PEST sequence and Proline-rich region (ARPP), also known as Ankyrin repeat domain-containing protein 2, is a protein that in humans is encoded by the ANKRD2 gene. ARPP is a member of the muscle ankyrin repeat proteins (MARP), which also includes CARP and DARP, and is highly expressed in cardiac and skeletal muscle and in other tissues. Expression of ARPP has been shown to be altered in patients with dilated cardiomyopathy and amyotrophic lateral sclerosis. A role for Ankrd2 in tumor progression and metastases spreading has also been described. ==Structure== Two isoforms of ARPP have been documented; a 39.8 kDa protein isoform composed of 360 amino acids and a 36.2 kDa protein isoform composed of 327 amino acids. ANKRD2 has nine exons, four of which encode ankyrin repeats in the middle region of the protein, a PEST-like and Lysine-rich sequence in the N-terminal region, and a Proline-rich sequence containing consensus sequences for phosphorylation in the C-terminal region. It has been proposed that ARPP can homo- or hetero-dimerize with other MARPs in an antiparallel fashion. ARPP is highly expressed in nuclei and I-bands in slow skeletal fibers and cardiac muscle, specifically in ventricular regions at intercalated discs; and expression in brain, pancreas and esophageal epithelium has also been documented. Though ARPP and CARP proteins show significant homology, their expression profiles in muscle cells are markedly different; CARP is expressed throughout atria and ventricles, in development and in adult myocytes, however ARPP is almost exclusively ventricular and only in adult myocytes. ARPP was also found to be expressed in rhabdomyosarcomas, exhibiting a pattern distinct from actin and desmin. ==Clinical Significance== In patients with dilated cardiomyopathy, levels of ARPP were upregulated. ARPP expression patterns have been shown to be altered in patients with amyotrophic lateral sclerosis (ALS), with decreased expression in slow skeletal muscle fibers and increased expression in fast skeletal muscle fibers. ARPP has also been shown to be a potentially useful biomarker for the differential diagnosis between oncocytoma and chromophobe renal cell carcinomas. In non-pathologic physiology, ARPP mRNA expression in skeletal muscle of patients was shown to be elevated two days following fatiguing jumping exercises. Levels of CARP, MLP and calpain-2 mRNA levels were also enhanced, suggesting that these molecules may be part of a signaling network activated by physical exercise. Ankrd2 has been shown to be involved in the progression of some types of cancers, such as osteosarcoma and head and neck squamous cell carcinoma. ==External links==

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