Induction of a massive endoplasmic reticulum and perinuclear space expansion by expression of lamin B receptor mutants and the related sterol reductases TM7SF2 and DHCR7.
Lamin B receptor (LBR) is an inner nuclear membrane protein involved in tethering the nuclear lamina and the underlying chromatin to the nuclear envelope. In addition, LBR exhibits sterol reductase activity. Mutations in the LBR gene cause two different human diseases: Pelger-Huët anomaly and Greenberg skeletal dysplasia, a severe chrondrodystrophy causing embryonic death. Our study aimed at investigating the effect of five LBR disease mutants on human cultured cells. Three of the tested LBR mutants caused a massive compaction of chromatin coincidental with the formation of a large nucleus-associated vacuole (NAV) in several human cultured cell lines. Live cell imaging and electron microscopy revealed that this structure was generated by the separation of the inner and outer nuclear membrane. During NAV formation, nuclear pore complexes and components of the linker of nucleoskeleton and cytoskeleton complex were lost in areas of membrane separation. Concomitantly, a large number of smaller vacuoles formed throughout the cytoplasm. Notably, forced expression of the two structurally related sterol reductases transmembrane 7 superfamily member 2 and 7-dehydrocholesterol reductase caused, even in their wild-type form, a comparable phenotype in susceptible cell lines. Hence, LBR mutant variants and sterol reductases can severely interfere with the regular organization of the nuclear envelope and the endoplasmic reticulum.
Zwerger
Monika
M
Department of Molecular Genetics, German Cancer Research Center, 69120 Heidelberg, Germany.
Kolb
Thorsten
T
Richter
Karsten
K
Karakesisoglou
Iakowos
I
Herrmann
Harald
H
D000199:Actins / Q000378:metabolism; D000596:Amino Acids / Q000378:metabolism; D017209:Apoptosis; D001343:Autophagy; D002460:Cell Line; D002467:Cell Nucleus / Q000201:enzymology* / Q000648:ultrastructure; D002470:Cell Survival; D002784:Cholesterol / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000201:enzymology* / Q000648:ultrastructure; D006801:Humans; D034882:Lamins / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism*; D008870:Microtubules / Q000378:metabolism / Q000648:ultrastructure; D050505:Mutant Proteins / Q000378:metabolism*; D028861:Nuclear Pore Complex Proteins / Q000378:metabolism; D044925:Oxidoreductases Acting on CH-CH Group Donors / Q000378:metabolism*; D010641:Phenotype; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D013312:Stress, Physiological; D014162:Transfection; D014617:Vacuoles / Q000378:metabolism / Q000648:ultrastructure; D000097682:Lamin B Receptor
D000199:Actins; D000596:Amino Acids; D002784:Cholesterol; D034882:Lamins; D008565:Membrane Proteins; D050505:Mutant Proteins; D028861:Nuclear Pore Complex Proteins; D044925:Oxidoreductases Acting on CH-CH Group Donors; D018160:Receptors, Cytoplasmic and Nuclear; D011993:Recombinant Fusion Proteins; D000097682:Lamin B Receptor; C019995:7-dehydrocholesterol reductase; C113387:TM7SF2 protein, human