Microtubule inner protein (MIP) part of the dynein-decorated doublet microtubules (DMTs) in cilia axoneme, which is required for motile cilia beating (By similarity). Suppresses cell death induced by accumulation of unfolded Pael receptor (Pael-R, a substrate of Parkin). Facilitates the formation of inclusions consisting of Pael-R, molecular chaperones, protein degradation molecules and itself when proteasome is inhibited. May play an important role in the formation of Lewy bodies and protection of dopaminergic neurons against Parkinson disease (PubMed:14532270). Forms a large molecular chaperone complex containing heat shock proteins 70 and 90 and chaperonin components. Interacts with STIP1, PRKN, GPR37, HSPA8, TCP1/CCT1, CCT2, CCT3, CCT4, CCT5, CCT6A, CCT7, CCT8. Interacts with MEIG1 (By similarity). Expressed in all immune tissues, spleen, lymph nodes, thymus, tonsils, leukocyte and bone marrow. Expressed also in heart, brain, skeletal muscle, kidney, lung and pancreas. Expressed in primary Schwann cells and very weakly by monocyte-derived macrophages the primary host cells of Mycobacterium leprae, the causative agent of leprosy. Component of Lewy bodies, intraneuronal inclusions found in the brain of Parkinson disease patients. Involved in susceptibility to leprosy (LPRS2) [MIM:607572]. LPRS2 is associated with polymorphisms in the 5'-regulatory region shared by the PRKN gene. Linked to PRKN in a head-to-head arrangement on opposite DNA strands and share a common 5'-flanking promoter region. May be due to exon skipping.