Roles of head and tail domains in alpha-internexin's self-assembly and coassembly with the neurofilament triplet proteins.
The roles of the head and tail domains of alpha-internexin, a type IV neuronal intermediate filament protein, in its self-assembly and coassemblies with neurofilament triplet proteins, were examined by transient transfections with deletion mutants in a non-neuronal cell line lacking an endogenous cytoplasmic intermediate filament network. The results from the self-assembly studies showed that the head domain was essential for alpha-internexin's ability to self-assemble into a filament network and the tail domain was important for establishing a proper filament network. The data from the coassembly studies demonstrated that alpha-internexin interacted differentially with the neurofilament triplet protein subunits. Wild-type NF-L or NF-M, but not NF-H, was able to complement and form a normal filament network with the tailless alpha-internexin mutant, the alpha-internexin head-deletion mutant, or the alpha-internexin mutant missing the entire tail and some amino-terminal portion of the head domain. In contrast, neither the tailless NF-L mutant nor the NF-L head-deletion mutant was able to form a normal filament network with any of these alpha-internexin deletion mutants. However, coassembly of the tailless NF-M mutant with the alpha-internexin head-deletion mutant and coassembly of the NF-M head-deletion mutant with the tailless alpha-internexin mutant resulted in the formation of a normal filament network. Thus, the coassembly between alpha-internexin and NF-M exhibits some unique characteristics previously not observed with other intermediate filament proteins: only one intact tail and one intact head are required for the formation of a normal filament network, and they can be present within the same partner or separately in two partners.
Ching
G Y
GY
Department of Pathology, Columbia University College of Physicians and Surgeons, New York, NY 10032, USA.
Liem
R K
RK
D008841:Actin Cytoskeleton / Q000378:metabolism; D000596:Amino Acids / Q000378:metabolism; D002352:Carrier Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D007381:Intermediate Filament Proteins; D016900:Neurofilament Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017384:Sequence Deletion; D013329:Structure-Activity Relationship; D014407:Tumor Cells, Cultured
D000596:Amino Acids; D002352:Carrier Proteins; D007381:Intermediate Filament Proteins; D016900:Neurofilament Proteins; C046643:alpha-internexin