Plays an indispensable role in the organization of KRT8/KRT18 filaments. Acts as an endogenous molecular chaperone for neuronal proteins including huntingtin. Suppresses aggregation and toxicity of polyglutamine-containing, aggregation-prone proteins. Isoform B but not isoform A inhibits huntingtin aggregation. Has a stimulatory effect on the ATPase activity of HSP70 in a dose-dependent and time-dependent manner and hence acts as a co-chaperone of HSP70. Also reduces cellular toxicity and caspase-3 activity.
Widely expressed. Highest levels in testis and brain, and lower levels in heart, spleen, intestine, ovary, placenta, lung, kidney, pancreas, thymus, prostate, skeletal muscle, liver and leukocytes. In testis, expressed in germ cells in the earlier stages of differentiation pathway as well as in spermatids. In brain, expressed at a higher level in hippocampus and thalamus and a lower level in amygdala, substantia nigra, corpus callosum and caudate nucleus.
Involvement in disease
Limb-girdle muscular dystrophy 1E
Contains 1 J domain.
The antiaggregation activity of isoform B resides in the serine-rich region and the C-terminus.
Cytoplasm, perinuclear region. Nucleus. Cytoplasm, myofibril, sarcomere, Z line.