FunctionIsoform 2 inhibits the ubiquitin ligase activity of SIAH1 and inhibits proteasomal degradation of target proteins. Isoform 2 inhibits autoubiquitination and proteasomal degradation of SIAH1, and thereby increases cellular levels of SIAH. Isoform 2 modulates SNCA monoubiquitination by SIAH1.
Tissue specificityDetected in brain (at protein level). Widely expressed, with highest levels in brain, heart and placenta.
Involvement in diseaseParkinson disease
Sequence similaritiesContains 6 ANK repeats.
Post-translational modificationsUbiquitinated; mediated by SIAH1, SIAH2 or RNF19A and leading to its subsequent proteasomal degradation. In the absence of proteasomal degradation, ubiquitinated SNCAIP accumulates in cytoplasmic inclusion bodies. Isoform 2 is subject to limited ubiquitination that does not lead to proteasomal degradation.
Cellular localizationCytoplasm. Detected in cytoplasmic inclusion bodies, together with SNCA.