title: Premature senescence in cells from patients with autosomal recessive hypercholesterolemia (ARH): evidence for a role for ARH in mitosis.
abstract: OBJECTIVE
  The defective gene causing autosomal recessive hypercholesterolemia (ARH) encodes ARH, a clathrin-associated adaptor protein required for low-density-lipoprotein receptor endocytosis in most cells but not in skin fibroblasts. The aim here was to elucidate why ARH fibroblasts grow slowly and undergo premature senescence.
  
  
  RESULTS
  Knockdown of ARH by RNA interference in IMR90 cells produces the same phenotype, indicated by increased p16 expression, γ-H2AX-positive foci, and enlarged flattened morphology. We showed that ARH contributes to several aspects of mitosis: it localizes to mitotic microtubules, with lamin B1 on the nuclear envelope and spindle matrix, and with clathrin heavy chain on mitotic spindles. Second, ARH is phosphorylated in G(2)/M phase by a roscovitine-sensitive kinase, probably cdc2. Third, cells lacking ARH show disfigured nuclei and defective mitotic spindles. Defects are most marked in ARH W22X cells, where translation starts at Met46, so the protein lacks a phosphorylation site at Ser14, identified by mass spectrometry of wild-type ARH.
  
  
  CONCLUSIONS
  The ARH protein is involved in cell cycle progression, possibly by affecting nuclear membrane formation through interaction with lamin B1 or other mitotic proteins, and its absence affects cell proliferation and induces premature senescence, which may play a role in the development of atherosclerosis in ARH.
authors.affiliation: Medical Research Council Clinical Sciences Centre, Imperial College London, Hammersmith Hospital, United Kingdom.
authors.forename: Xi-Ming
authors.initials: XM
authors.lastname: Sun
authors.forename: Dilip D
authors.initials: DD
authors.lastname: Patel
authors.forename: Juan-Carlos
authors.initials: JC
authors.lastname: Acosta
authors.forename: Jesùs
authors.initials: J
authors.lastname: Gil
authors.forename: Anne K
authors.initials: AK
authors.lastname: Soutar
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics / Q000378:metabolism*; D050197:Atherosclerosis / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D016203:CDC2 Protein Kinase; D016022:Case-Control Studies; D053144:Cell Nucleus Shape; D049109:Cell Proliferation; D048430:Cell Shape; D016922:Cellular Senescence / Q000235:genetics; D019926:Cyclin B / Q000378:metabolism; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000378:metabolism; D018844:Cyclin-Dependent Kinases; D005347:Fibroblasts / Q000378:metabolism* / Q000473:pathology; D005838:Genotype; D006367:HeLa Cells; D006657:Histones / Q000378:metabolism; D006801:Humans; D006937:Hypercholesterolemia / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D034921:Lamin Type B / Q000378:metabolism; D013058:Mass Spectrometry; D008870:Microtubules / Q000378:metabolism; D008938:Mitosis / Q000235:genetics; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D009685:Nuclear Envelope / Q000378:metabolism; D010641:Phenotype; D010766:Phosphorylation; D034622:RNA Interference; D012867:Skin / Q000378:metabolism* / Q000473:pathology; D008941:Spindle Apparatus / Q000378:metabolism; D013997:Time Factors; D014162:Transfection
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D019926:Cyclin B; D019941:Cyclin-Dependent Kinase Inhibitor p16; C468783:H2AX protein, human; D006657:Histones; C469745:LDLRAP1 protein, human; D034921:Lamin Type B; D016203:CDC2 Protein Kinase; C528899:CDK1 protein, human; D018844:Cyclin-Dependent Kinases