Dependence of diffusional mobility of integral inner nuclear membrane proteins on A-type lamins.
Integral proteins of the nuclear envelope inner membrane have been proposed to reach their sites by diffusion after their co-translational insertion in the rough endoplasmic reticulum. They are then retained in the inner nuclear membrane by binding to nuclear structures. One such structure is the nuclear lamina, an intermediate filament meshwork composed of A-type and B-type lamin proteins. Emerin, MAN1, and LBR are three integral inner nuclear membrane proteins. We expressed these proteins fused to green fluorescent protein in embryonic fibroblasts from wild-type mice and Lmna -/- mice, which lack A-type lamins. We then studied the diffusional mobilities of emerin, MAN1, and LBR using fluorescence recovery after photobleaching. We show that emerin and MAN1, but not LBR, are more mobile in the inner nuclear membrane of cells from Lmna -/- mice than in cells from wild-type mice. In cells from Lmna -/- mice expressing exogenous lamin A, the protein mobilities were similar to those in cells from wild-type mice. This supports a model where emerin and MAN1 are at least partly retained in the inner nuclear membrane by binding to A-type lamins, while LBR depends on other binding partners for its retention.
Ostlund
Cecilia
C
Department of Medicine, College of Physicians and Surgeons, Columbia University, Room 10-509, 630 West 168th Street, New York, New York 10032, USA.
Sullivan
Teresa
T
Stewart
Colin L
CL
Worman
Howard J
HJ
D000818:Animals; D002478:Cells, Cultured; D004058:Diffusion; D004622:Embryo, Mammalian / Q000502:physiology; D004721:Endoplasmic Reticulum / Q000502:physiology; D005347:Fibroblasts / Q000502:physiology; D036681:Fluorescence Recovery After Photobleaching / Q000379:methods; D020869:Gene Expression Profiling; D049452:Green Fluorescent Proteins / Q000502:physiology; D034904:Lamin Type A / Q000378:metabolism / Q000502:physiology*; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D051379:Mice; D018345:Mice, Knockout; D009685:Nuclear Envelope / Q000378:metabolism*; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D018160:Receptors, Cytoplasmic and Nuclear / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D013946:Thymopoietins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D013997:Time Factors; D000097682:Lamin B Receptor
D049452:Green Fluorescent Proteins; D034904:Lamin Type A; D008565:Membrane Proteins; D009687:Nuclear Proteins; D018160:Receptors, Cytoplasmic and Nuclear; D011994:Recombinant Proteins; D013946:Thymopoietins; D000097682:Lamin B Receptor; C092710:emerin