Alpha-crystallin domain (ACD) found in mammalian 21.6 KDa small heat shock protein (sHsp) HspB8, also denoted as Hsp22 in humans, and similar proteins. sHsps are molecular chaperones that suppress protein aggregation and protect against cell stress, and are generally active as large oligomers consisting of multiple subunits. A chaperone complex formed of HspB8 and Bag3 stimulates degradation of protein complexes by macroautophagy. HspB8 also forms complexes with Hsp27 (HspB1), MKBP (HspB2), HspB3, alphaB-crystallin (HspB5), Hsp20 (HspB6), and cvHsp (HspB7). These latter interactions may depend on phosphorylation of the respective partner sHsp. HspB8 may participate in the regulation of cell proliferation, cardiac hypertrophy, apoptosis, and carcinogenesis. Point mutations in HspB8 have been correlated with the development of several congenital neurological diseases, including Charcot Marie tooth disease and distal motor neuropathy type II.