The inner nuclear membrane protein Sun1 mediates the anchorage of Nesprin-2 to the nuclear envelope
Padmakumar VC, Libotte T, Lu W, Zaim H, Abraham S, Noegel AA, Gotzmann J, Foisner R and Karakesisoglou I
J Cell Sci
Cancer Research/Cell Biology
Cells used in publication:
Tissue Origin: dermal
Nesprins form a novel class of nuclear envelope-anchored spectrin-repeat proteins. We show that a direct association of their highly conserved C-terminal luminal domain with the inner nuclear membrane protein Sun1 mediates their nuclear envelope localisation. In Nesprin-1 and Nesprin-2 the conserved C-terminal amino acids PPPX are essential for the interaction with a C-terminal region in Sun1. In fact, Sun1 is required for the proper nuclear envelope localisation of Nesprin-2 as shown using dominant-negative mutants and by knockdown of Sun1 expression. Sun1 itself does not require functional A-type lamins for its localisation at the inner nuclear membrane in mammalian cells. Our findings propose a conserved nuclear anchorage mechanism between Caenorhabditis elegans and mammals and suggest a model in which Sun1 serves as a ;structural bridge' connecting the nuclear interior with the actin cytoskeleton.
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