Recombinant Human α-Internexin Cat# Prot-r-a-Int

      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).

      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, 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 T, 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).