Internexin Neuronal Intermediate Filament Protein Alpha (INa)

Neurofilaments (NFs) are the cytoplasmic intermediate filaments (IFs) found in neurons. IF proteins have 3 distinct regions: head, rod, and tail.The deduced 494-amino acid INA protein is 90% homologous with the rat sequence, although it is shorter in that it contains 6 rather than 10 glu residues. Northern blot analysis detected intense expression of a 3.2-kb INA transcript in fetal brain and in an adrenergic, but not in an adrenergic and cholinergic, tumor cell line. RNase protection analysis determined that INA is expressed at week 16, with rapid increases until it reaches a steady state at week 18. In contrast, NEFL was readily detectable only at week 18, and NEFM was not detectable through week 24. Restriction enzyme and Southern blot analysis indicated that INA is a single-copy gene.