α-Internexin protein, Cat# Prot-r-a-Int
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α-internexin is a Class IV intermediate filament originally discovered as it copurifies with other neurofilament subunits (1). α-internexin is related to but distinct from the better known neurofilament triplet proteins, NF-L, NF-M and NF-H, having similar protein sequence motifs and a similar intron organization. It is expressed only in neurons and in large amounts early in neuronal development, but is down-regulated in many neurons as development proceeds. On SDS-PAGE gels it runs with an apparent molecular weight of 64 to 66 kDa, with some species variability, although the real molecular weight is about 55 kDa. As with other neurofilament subunits the presence of highly negatively charged sequences results in reduction of SDS-PAGE mobility.
Many classes of mature neurons contain α-internexin in addition to NF-L, NF-M and NF-H. In some mature neurons α-internexin is the only neurofilament subunit expressed. Antibodies to α-internexin are therefore unique probes to study and classify neuronal types and follow their processes in sections and in tissue culture. In addition the very early developmental expression of α-internexin means its presence is an early and convenient diagnostic feature of neuronal progenitors cells and other cell committed to the neuronal lineage. In addition recent studies show a marked up-regulation of α-internexin during neuronal regeneration (2). The use of antibodies to this protein in the study of brain tumors has not been examined to date, but is likely to be of interest. Antibody to this protein show that α-internexin is an abundant component of the inclusions of neurofilament inclusion body disease (NFID), a serious human neurodegenerative disorder (3).
Coomassie brilliant blue stained SDS-PAGE gel of various recombinant proteins. His-tagged human α-Internexin, was expressed and purified from
BL21 using immobilized metal affinity chromatography. 1 µg of protein was run on each lane, and the lane indicated with “α-Int” contains the α-Internexin protein. The other lanes show recombinant His-tagged peripherin, vimentin and NF-L as indicated. Protein molecular weight standards are in the first lane and apparent molecular weights are as indicated.
A cDNA encoding full length human α-Internexin was inserted into a eukaryotic expression vector which adds an N-terminal in frame His-tag. This was transformed into <em>E. coli</em> and recombinant protein was purified in 6M urea using immobilized metal affinity chromatography. Purified protein was diluted to 1 mg/mL and is supplied in 6M urea.
1. Pachter, J and Liem, RKH. Alpha-Internexin, a 66-kD intermediate filament-binding protein from mammalian central nervous tissues.
J Cell Biol 101:1316-22 (1985)
2. McGraw et al. Axonally transported peripheral signals regulate alpha-internexin expression in regenerating motorneurons.
J Neurosci 22:4955-63 (2002)
3. Cairns NJ et al. alpha-internexin is present in the pathological inclusions of neuronal intermediate filament inclusion disease.
Am J Pathol. 164:2153-61 (2004).
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