Emerin caps the pointed end of actin filaments: evidence for an actin cortical network at the nuclear inner membrane.
X-linked Emery-Dreifuss muscular dystrophy is caused by loss of emerin, a LEM-domain protein of the nuclear inner membrane. To better understand emerin function, we used affinity chromatography to purify emerin-binding proteins from nuclear extracts of HeLa cells. Complexes that included actin, alphaII-spectrin and additional proteins, bound specifically to emerin. Actin polymerization assays in the presence or absence of gelsolin or capping protein showed that emerin binds and stabilizes the pointed end of actin filaments, increasing the actin polymerization rate 4- to 12-fold. We propose that emerin contributes to the formation of an actin-based cortical network at the nuclear inner membrane, conceptually analogous to the actin cortical network at the plasma membrane. Thus, in addition to disrupting transcription factors that bind emerin, loss of emerin may destabilize nuclear envelope architecture by weakening a nuclear actin network.
Holaska
James M
JM
Department of Cell Biology, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.
Kowalski
Amy K
AK
Wilson
Katherine L
KL
D008841:Actin Cytoskeleton / Q000737:chemistry*; D000199:Actins / Q000737:chemistry*; D001665:Binding Sites; D002462:Cell Membrane / Q000378:metabolism; D002467:Cell Nucleus / Q000378:metabolism*; D002846:Chromatography, Affinity; D018260:Gelsolin / Q000737:chemistry; D006367:HeLa Cells; D006801:Humans; D008565:Membrane Proteins / Q000737:chemistry*; D009136:Muscular Dystrophies / Q000473:pathology; D009685:Nuclear Envelope / Q000378:metabolism*; D009687:Nuclear Proteins; D011485:Protein Binding; D013946:Thymopoietins / Q000737:chemistry*; D014158:Transcription, Genetic
D000199:Actins; D018260:Gelsolin; D008565:Membrane Proteins; D009687:Nuclear Proteins; D013946:Thymopoietins; C092710:emerin