Type IV neuronal intermediate filament proteins consist of alpha-internexin, which can self-assemble into filaments and the neurofilament triplet proteins, which are obligate heteropolymers, at least in rodents. These IF proteins therefore provide good systems for elucidating the mechanism of intermediate filament assembly. To analyze the roles of the head domains of these proteins in contributing to their differential assembly properties, we generated chimeric proteins by swapping the head domains between @entity35 alpha-internexin and either @entity35 @entity18423 or @entity18424 and examined their assembly properties in transfected cells that lack their own cytoplasmic intermediate filament network. Lalphaalpha and Malphaalpha, the chimeric proteins generated by replacing the head domain of alpha-internexin with those of @entity18423 and @entity18424 , respectively, were unable to self-assemble into filaments. In contrast, alphaLL, a chimeric @entity18423 protein generated by replacing the head domain of @entity18423 with that of alpha-internexin, was able to self-assemble into filaments, whereas @entity37243 , a chimeric @entity18423 protein containing the @entity18424 head domain, was unable to do so. These results demonstrate that the alpha-internexin head domain is essential for alpha-internexin's ability to self-assemble. While coassembly of Lalphaalpha with @entity18424 and coassembly of Malphaalpha with @entity18423 resulted in formation of filaments, coassembly of Lalphaalpha with @entity18423 and coassembly of Malphaalpha with @entity18424 yielded punctate patterns. These coassembly results show that heteropolymeric filament formation requires that one partner has the @entity18423 head domain and the other partner has the @entity18424 head domain. Thus, the head domains of @entity35 @entity18423 and @entity18424 play important roles in determining the obligate heteropolymeric nature of filament formation. The data obtained from these self-assembly and coassembly studies provide some new insights into the mechanism of intermediate filament assembly.

Analysis of the roles of the head domains of type IV XXXX neuronal intermediate filament proteins in filament assembly using domain-swapped chimeric proteins.

@entity35 :: ('10116', 'Species') :: ['rat'] @entity18424 :: ('24588(Tax:10116)', 'Gene') :: ['NF-M'] @entity18423 :: ('83613(Tax:10116)', 'Gene') :: ['NF-L'] @entity37243 :: ('315606(Tax:10116)', 'Gene') :: ['MLL']
@entity35 :: (10116,Species) :: ['rat']
