HIP12 is a non-proapoptotic member of a gene family including HIP1, an interacting protein with huntingtin

Huntingtin-interacting protein 1 (HIP1) is a membrane-associated protein that interacts with huntingtin, the protein altered in Huntington disease. HIP1 shows homology to S1a2p, a protein essential for the assembly and function of the cytoskeleton and endocytosis in Saccharomyces cerevisiae. We have determined that the HIP1 gene comprises 32 exons spanning approximately 215 kb of genomic DNA and gives rise to two alternate splice forms termed HIP1-1 and HIP1-2. Additionally, we have identified a novel protein termed HIP12 with significant sequence and biochemical similarities to HIP1 and high sequence similarity to S1a2p. HIP12 differs from HIP1 in its pattern of expression both at the mRNA and protein level. However, HIP1 and HIP12 are both found within the brain and show a similar subcellular distribution pattern. In contrast to HIP1, which is toxic in cell culture, HIP12 does not confer toxicity in the same assay systems. Interestingly, HIP12 does not interact with huntingtin but can interact with HIP 1, suggesting a potential interaction in vivo that may influence the function of each respective protein.