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Human Sun2-KASH5 complex
Structural highlights
FunctionSUN2_HUMAN Component of SUN-protein-containing multivariate complexes also called LINC complexes which link the nucleoskeleton and cytoskeleton by providing versatile outer nuclear membrane attachment sites for cytoskeletal filaments. Specifically, SYNE2 and SUN2 assemble in arrays of transmembrane actin-associated nuclear (TAN) lines which are bound to F-actin cables and couple the nucleus to retrograde actin flow during actin-dependent nuclear movement. Required for interkinetic nuclear migration (INM) and essential for nucleokinesis and centrosome-nucleus coupling during radial neuronal migration in the cerebral cortex and during glial migration. Anchors chromosome movement in the prophase of meiosis and is involved in selective gene expression of coding and non-coding RNAs needed for gametogenesis. Required for telomere attachment to nuclear envelope and gametogenesis. May also function on endocytic vesicles as a receptor for RAB5-GDP and participate in the activation of RAB5.[1] Publication Abstract from PubMedLinker of nucleoskeleton and cytoskeleton (LINC) complexes are molecular tethers that span the nuclear envelope (NE) and physically connect the nucleus to the cytoskeleton. They transmit mechanical force across the NE in processes such as nuclear anchorage, nuclear migration, and homologous chromosome pairing during meiosis. LINC complexes are composed of KASH proteins traversing the outer nuclear membrane, and SUN proteins crossing the inner nuclear membrane. Humans have several SUN- and KASH-containing proteins, yet what governs their proper engagement is poorly understood. To investigate this question, we solved high resolution crystal structures of human SUN2 in complex with the KASH-peptides of Nesprin3, Nesprin4, and KASH5. In comparison to the published structures of SUN2-KASH1/2 we observe alternative binding modes for these KASH peptides. While the core interactions between SUN and the C-terminal residues of the KASH peptide are similar in all five complexes, the extended KASH-peptide adopts at least two different conformations. The much-improved resolution allows for a more detailed analysis of other elements critical for KASH interaction, including the KASH-lid and the cation loop, and a possible self-locked state for unbound SUN. In summary, we observe distinct differences between the examined SUN-KASH complexes. These differences may have an important role in regulating the SUN-KASH network. Structural Analysis of Different LINC Complexes Reveals Distinct Binding Modes.,Cruz VE, Esra Demircioglu F, Schwartz TU J Mol Biol. 2020 Oct 12;432(23):6028-6041. doi: 10.1016/j.jmb.2020.09.019. PMID:33058875[2] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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