HSPB2, also known as MKBP is the most divergent member of the sHSP family with only 30% sequence identity to all other mammalian sHSPS (1). MKBP is known to associate specifically with myotonic dystrophy protein kinase (DMPK) in skeletal muscle. MKBP enhances the kinase activity of DMPK and protects it from heat-induced activation. MKBP also shows a unique nature compared to other sHSps, in that the expression of MKBP is not induced by heat shock (2). In unstressed skeletal muscle, MKBP forms large oligomeric complexes with HSPB3 in the cytosol which are localized on mitochondria and the neuromuscular junction (1, 3). During stress, these complexes dissolve and MKBP’s localization to mitochondria increases, leading to increased cell survival. Pinz et al. tried to find a distinct role for MKBP in terms of cardiac mechanics and finds that it is required for normal systolic performance and normal cardiac energetic (1).
HSPB2 has also been found to be expressed in several cancer cell lines, including human breast cancer, suggesting that MKBP may be an important factor in tumor transformation and metastasis (4).