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Huntingtin is a protein, present in human cells. An abnormal form of the protein is associated with Huntington's Disease.
Introduction
Huntingtin (Htt) is the protein coded by the HD gene. It is very variable in its structure, with regard to the number of glutamine residues present, due to the large number of polymorphisms of the HD gene. In its wild-type (normal) form, it contains 6-34 glutamine residues. In individuals affected by Huntington's Disease, an autosomal dominant genetic disorder, it contains between 35-155 glutamine residues. Huntingtin has a predicted mass of ~350kDa, however, this varies and is largely dependent on the number of glutamine residues in the protein.
Function
The function of Huntingtin is unclear. It has however been experimentally demonstrated that Huntingtin acts as a transcription factor in upregulating the expression of Brain Derived Neurotrophic Factor (BDNF). In the deficient protein, there is supression of this transcription regulatory function of Huntingtin and hence underexpression of BDNF.
From immunohistochemistry, electron microscopy, subcellular fractionation studies of the molecule, it has been found that Huntingtin is primarily associated with vesicles and/or microtubules. These appear to indicate a functional role in cytoskeletal anchoring or transport of mitochondria.
Huntingtin has also been found to interact with a number of proteins. One such protein is the Huntingtin Interacting Protein I (HIP-I/Hip-1). Unfortunately the actions mediated via these interactions of huntingtin with the complementary interacting proteins is not fully understood.
References
1. Wanker EE, Rovira C, Scherzinger E, Hasenbank R, Walter S, Tait D, Colicelli J, Lehrach H, HIP-I: a huntingtin interacting protein isolated by the yeast two-hybrid system, Hum Mol Genet. 1997 Mar;6(3):487-95
2. Zuccato C, Ciammola A, Rigamonti D, Leavitt BR, Goffredo D, Conti L, MacDonald ME, Friedlander RM, Silani V, Hayden MR, Timmusk T, Sipione S, Cattaneo E., Loss of huntingtin-mediated BDNF gene transcription in Huntington's disease, Science. 2001 Jul 20;293(5529):445-6.
External links
"Huntingtin"