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. Homooligomer. Interacts with BAG3, HSPB8 and STUB1. Interacts with ALKBH1 (By similarity). Interacts with HSP70, KRT18 and PTTG. Isoform B interacts with histone deacetylases HDAC4, HDAC6, and SIRT2, HDAC activity is required for antiaggregation. 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. The antiaggregation activity of isoform B resides in the serine-rich region and the C-terminus. The disease is caused by variants affecting the gene represented in this entry. There is evidence that LGMDD1 is caused by dysfunction of isoform B (PubMed:22366786).