Nuclear envelope organization in Dictyostelium discoideum

Abstract

The nuclear envelope consists of the outer and the inner nuclear membrane, the nuclear lamina and the nuclear pore complexes, which regulate nuclear import and export. The major constituent of the nuclear lamina of Dictyostelium is the lamin NE81. It can form filaments like B-type lamins and it interacts with Sun1, as well as with the LEM/HeH-family protein Src1. Sun1 and Src1 are nuclear envelope transmembrane proteins involved in the centrosome-nucleus connection and nuclear envelope stability at the nucleolar regions, respectively. In conjunction with a KASH-domain protein, Sun1 usually forms a so-called LINC complex. Two proteins with functions reminiscent of KASH-domain proteins at the outer nuclear membrane of Dictyostelium are known; interaptin which serves as an actin connector and the kinesin Kif9 which plays a role in the microtubule-centrosome connector. However, both of these lack the conserved KASH-domain. The link of the centrosome to the nuclear envelope is essential for the insertion of the centrosome into the nuclear envelope and the appropriate spindle formation. Moreover, centrosome insertion is involved in permeabilization of the mitotic nucleus, which ensures access of tubulin dimers and spindle assembly factors. Our recent progress in identifying key molecular players at the nuclear envelope of Dictyostelium promises further insights into the mechanisms of nuclear envelope dynamics. , and build upon the material for any purpose, even commercially), providing you give appropriate credit, provide a link to the license, and indicate if changes were made. You may do so in any reasonable manner, but not in any way that suggests the licensor endorses you or your use. Printed in Spain Abbreviations used in this paper: BAF, barrier to autointegration factor; BioID, proximity-dependent biotin identification; CDK1, cyclin-dependent kinase 1; cryo-ET, cryo-electron tomography; DAPI, 4′,6-diamidin-2-phenylindol; EM, electron microscopy; ER, endoplasmic reticulum; ExM, expansion microscopy; feSEM, field-emission scanning electron microscopy; FRAP, fluorescence recovery after photobleaching; GFP, green fluorescent protein; HeH, helix-extension-helix; IF, intermediate filament; INM, inner nuclear membrane; KASH, Klarsicht, ANC-1, Syne Homology; LBR, lamin B receptor; LECA, last eukaryotic common ancestor; LEM, lamina-associated polypeptide 2 (LAP2), Emerin, and MAN1; LINC, linker of the nucleoskeleton and the cytoskeleton; MCAK, mitotic centromere-associated kinesin; MEF, mouse embryonic fibroblast; NET, nuclear envelope transmembrane protein; NLS, nuclear localization sequence; NPC, nuclear pore complex; ONM, outer nuclear membrane; STED, stimulated emission depletion. import and export. On its nuclear side, the INM is associated with a fibrous, so-called nuclear lamina. Among the NETs, the Sun-domain proteins in the INM (e.g. Sun1) and KASH-domain proteins in the ONM (e.g. nesprin) have to be highlighted, as they form the so-called LINC complex, which spans the whole nuclear envelope (Lee and Burke, 2018...

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