Nesprin-3, a novel outer nuclear membrane protein, associates with the cytoskeletal linker protein plectin

Abstract

Despite their importance in cell biology, the mechanisms that maintain the nucleus in its proper position in the cell are not well understood. This is primarily the result of an incomplete knowledge of the proteins in the outer nuclear membrane (ONM) that are able to associate with the different cytoskeletal systems. Two related ONM proteins, nuclear envelope spectrin repeat (nesprin)–1 and –2, are known to make direct connections with the actin cytoskeleton through their NH2-terminal actin-binding domain (ABD). We have now isolated a third member of the nesprin family that lacks an ABD and instead binds to the plakin family member plectin, which can associate with the intermediate filament (IF) system. Overexpression of nesprin-3 results in a dramatic recruitment of plectin to the nuclear perimeter, which is where these two molecules are colocalized with both keratin-6 and -14. Importantly, plectin binds to the integrin α6β4 at the cell surface and to nesprin-3 at the ONM in keratinocytes, suggesting that there is a continuous connection between the nucleus and the extracellular matrix through the IF cytoskeleton.

LULL1 Retargets TorsinA to the Nuclear Envelope Revealing an Activity That Is Impaired by theDYT1Dystonia Mutation

“…The NE is the favored binding site for hydrolysis deficient "substrate trap" TorA mutants (Goodchild and Dauer, 2004;Naismith et al, 2004;Kock et al, 2006). Finally, the outer nuclear membrane protein nesprin-3 (Wilhelmsen et al, 2005) is abnormally distributed in fibroblasts from TorA knockout mice, and these cells move slower than controls in a polarized cell migration assay (Nery et al, 2008). Because nesprin-3 participates in linker of the nucleoskeleton and cytoskeleton (LINC) complexes (Wilhelmsen et al, 2005;Ketema et al, 2007;Crisp and Burke, 2008;StewartHutchinson et al, 2008;Starr, 2009), these data suggest that TorA activity may help regulate NE structure and connections between nucleus and cytoskeleton.…”

Diseases of epidermal keratins and their linker proteins

“…Plectin has a remarkable number of versatile binding affinities for other proteins, including keratins 5 and 14, vimentin, glial fibrillary acidic protein, the neurofilament protein triplet, and lamin B, suggesting that it can tether one filamentous network to another [44]. The binding of keratin intermediate filament to nucleus may involve binding of plectin to nesprin-3, an outer nuclear membrane protein (45). Although plectin is expressed in nearly all cell types, its precise cytoplasmic localization is cell-type specific, and it can appear diffusely throughout the cell as a cytomatrix component or in a restricted distribution as a focal adhesion protein.…”

“…For example, mutations in KTR5 or KRT14 genes have failed to be detected in up to ~30% of cases of EBS using conventional mutation screening and sequencing protocols. It is plausible that a large number of these families harbor mutations in keratin linker protein genes, such as the plectin gene [45], but some mutations may also reside in the keratin genes in the regions that are not routinely analyzed. Similarly, in approximately 25% of patients with desmosomal skin fragility disorders search for mutations in the known candidate genes has not been successful, suggesting that there may be additional, less characterized genes that may participate in cell-cell interactions.…”

Depletion of Nesprin-2 is associated with an embryonic lethal phenotype in mice

“…Furthermore, the SYNE1-4 genes give rise to a multitude of isoforms [10,11]. The presence of specific domains is responsible for their linkage to individual cytoskeletal elements, the actin filaments, microtubules or intermediate filaments [2,12–14]. The largest isoform of Nesprin-2, also known as NUANCE, is an ~ 800 kDa protein (6,885 amino acids) with an N-terminal F-actin binding domain (ABD), a rod domain composed of spectrin repeats and the C-terminal KASH domain[2].…”