Nesprin 4 is an outer nuclear membrane protein that can induce kinesin-mediated cell polarization

Abstract

Nucleocytoplasmic coupling is mediated by outer nuclear membrane (ONM) nesprin proteins and inner nuclear membrane Sun proteins. Interactions spanning the perinuclear space create nesprin-Sun complexes connecting the cytoskeleton to nuclear components. A search for proteins displaying a conserved C-terminal sequence present in nesprins 1-3 identified nesprin 4 (Nesp4), a new member of this family. Nesp4 is a kinesin-1-binding protein that displays Sun-dependent localization to the ONM. Expression of Nesp4 is associated with dramatic changes in cellular organization involving relocation of the centrosome and Golgi apparatus relative to the nucleus. These effects can be accounted for entirely by Nesp4's kinesin-binding function. The implication is that Nesp4 may contribute to microtubule-dependent nuclear positioning.centrosome ͉ LINC complex ͉ nuclear envelope T he nuclear envelope (NE) forms the interface between the nucleus and cytoplasm acting as a selective barrier that regulates nucleo-cytoplasmic traffic (1). In addition to this partition function, accumulating evidence reveals an essential role for the NE as a determinant of higher-order nuclear and chromatin organization (2). More surprising are findings that the NE directly impacts cytoskeletal architecture and in this way may help define the mechanical properties of the cell as a whole (3). The molecular bases for these effects are now emerging, uniting aspects of cellular physiology from mechanotransduction to nuclear positioning during differentiation and development (4).The NE is assembled from several elements, the most prominent being inner nuclear membranes (INMs) and outer nuclear membranes (ONMs) separated by a Ϸ40-nm gap or perinuclear space (PNS). The INM and ONM are joined where they are spanned by nuclear pore complexes (NPCs), the mediators of trafficking across the NE. The ONM also displays connections to the peripheral endoplasmic reticulum (ER). Accordingly, the INM, ONM, and ER represent a single membrane system with the PNS forming an extension of the ER lumen.The final feature of the NE is the nuclear lamina, a protein meshwork composed primarily of A-and B-type lamins that lines the nuclear face of the INM (2). The lamina is required for NE integrity and provides chromatin-anchoring sites at the nuclear periphery. Remarkably, aberrant A-type lamin expression, which is linked to several human diseases (5), is associated with altered cytoskeletal mechanics (3). The mechanisms underlying this phenomenon represent an intriguing biological problem.At least 60 NE membrane proteins are known (6). Although most likely reside in the INM, several ONM proteins have been identified (7). These include members of the mammalian nesprin (or syne) family (8, 9), Klarsicht (10) and 12) in Drosophila melanogaster, Anc-1 (13), and 16) in Caenorhabditis elegans, and Kms2 in the fission yeast Schizosaccharomyces pombe (17). A property that each of these has in common is that they interact with cytoskeletal components. They are also united in possessing a...

Dynamic JUNQ inclusion bodies are asymmetrically inherited in mammalian cell lines through the asymmetric partitioning of vimentin

“…3G and Fig. S2F) (27). Ectopic expression of Nesprin 4 caused a dislocation of the vimentin JUNQ away from the nucleus, together with the MTOC (Fig.…”

“…Perhaps mammalian inclusions are often perinuclear because that is where most of the cytosol is located? We devised a way of testing the robustness of the association between the inclusions and the MTOC using Nesprin 4 (27). Nesprin 4 is expressed in polarized cells and directs the movement of the MTOC away from the nucleus (Fig.…”

Spatial coordination between cell and nuclear shape within micropatterned endothelial cells

“…Furthermore, perturbations of the intermediate filament network could alter the positioning of the nucleus in both migrating and immobile astrocytes, suggesting that cytoplasmic intermediate filaments are involved in actin-dependent positioning of the nucleus 20 . Concomitant with these recent discoveries, significant advances have been made in terms of identifying the molecular links between the nuclear envelope and the cytoplasmic filaments [21][22][23][24][25] , and new insights have been gained into the mechanistic maintenance of the nucleus 3,23,24,26,27 . Emerging evidence is now accumulating that cytoplasmic filaments are exploited by cells to govern nuclear morphology and finely tune gene expression in response to cell shape changes.…”

Nuclear deformability and telomere dynamics are regulated by cell geometric constraints

“…Microtubules are physically coupled to the nucleus via LINC complex (51) and to actin via microtubuleactin crosslinking factors (MACFs) (52). To probe whether the microtubule network that surrounds the nucleus could transmit force for nuclear fluctuations, microtubules were depolymerized using nocodazole in cells on CI patterns.…”