Separation of Coiled-Coil Structures in Lamin A/C Is Required for the Elongation of the Filament

Abstract

Intermediate filaments (IFs) commonly have structural elements of a central α-helical coiled-coil domain consisting of coil 1a, coil 1b, coil 2, and their flanking linkers. Recently, the crystal structure of a long lamin A/C fragment was determined and showed detailed features of a tetrameric unit. The structure further suggested a new binding mode between tetramers, designated eA22, where a parallel overlap of coil 1a and coil 2 is the critical interaction. This study investigated the biochemical effects of genetic mutations causing human diseases, focusing on the eA22 interaction. The mutant proteins exhibited either weakened or augmented interactions between coil 1a and coil 2. The ensuing biochemical results indicated that the interaction requires the separation of the coiled-coils in the N-terminal of coil 1a and the C-terminal of coil 2, coupled with the structural transition in the central α-helical rod domain. This study provides insight into the role of coil 1a as a molecular regulator in the elongation of IF proteins.

Cyclin-dependent kinase 1 depolymerizes nuclear lamin filaments by disrupting the head-to-tail interaction of the lamin central rod domain

“…Our previous results further supported the four-helix bundle formation that the separation of coil 1a and the C-terminal part of coil 2 was required (33). The separation of the coiled-coils was needed for the structural transition from two coiled-coil dimers to the complex.…”

“…2). We noted the coil 1a region, which is adjacent to the phosphorylation sites because the coiled-coil tendency of the coil 1a region was reversely correlated to the ACN interactions in the L59R mutant (33,34).…”

“…Wild-type lamin 1-125 fragment (human lamin A/C, residues 1-125) and mutant forms (T19A, S22A, T19A/S22A, S22D, T19D/S22D, T10D/S12D/T19D/S22D, R25E/R28E) with an N-terminal hexaHis-tag were expressed in E. coli as previously described (33). Human lamin A/C 250-400 (coil 2C-containing fragment in the main text) was expressed in E. coli as an N-terminal GST-fusion protein.…”

Mice harboring a R133L heterozygous mutation in LMNA exhibited ectopic lipid accumulation, aging, and mitochondrial dysfunction in adipose tissue

“…Lamin A consists of a 42-residue lamin-specific 1B insert and constitutes almost half of the super-helix turn in the middle of the 1B domain, with which it preserves heptad periodicity for dimer formation, conserves the positions of the distal coiled-coil regions for tetramer formation, and provides additional interdimer molecular contacts. [6][7][8][9] Thus, mutations in the rod domain of lamin A could directly affect intermolecular interactions and/or protein stability, and may lead to progeroid laminopathies such as APS and A-WS. 9,10 Based on the phenotypic diversity and tissue-specific nature of the laminopathies, several studies have investigated the mechanisms underlying these diseases, which involve disruption of the protein structure due to lamin A mutations.…”

“…The rod domain was traditionally divided into four helical domains (coil 1A‐aa34‐70, coil‐1B‐aa80‐218, and coil‐2‐aa242‐283). Lamin A consists of a 42‐residue lamin‐specific 1B insert and constitutes almost half of the super‐helix turn in the middle of the 1B domain, with which it preserves heptad periodicity for dimer formation, conserves the positions of the distal coiled‐coil regions for tetramer formation, and provides additional interdimer molecular contacts 6–9 . Thus, mutations in the rod domain of lamin A could directly affect intermolecular interactions and/or protein stability, and may lead to progeroid laminopathies such as APS and A‐WS 9,10 …”