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Titolo:
Co-translational interactions of apoprotein B with the ribosome and translocon during lipoprotein assembly or targeting to the proteasome
Autore:
Pariyarath, R; Wang, HX; Aitchison, JD; Ginsberg, HN; Welch, WJ; Johnson, AE; Fisher, EA;
Indirizzi:
CUNY Mt Sinai Sch Med, Cardiovasc Inst, New York, NY 10029 USA CUNY Mt Sinai Sch Med New York NY USA 10029 Inst, New York, NY 10029 USA CUNY Mt Sinai Sch Med, Dept Med, New York, NY 10029 USA CUNY Mt Sinai Sch Med New York NY USA 10029 t Med, New York, NY 10029 USA CUNY Mt Sinai Sch Med, Dept Cell Biol & Anat, New York, NY 10029 USA CUNY Mt Sinai Sch Med New York NY USA 10029 Anat, New York, NY 10029 USA Univ Alberta, Dept Anat & Cell Biol, Edmonton, AB T6G 2H7, Canada Univ Alberta Edmonton AB Canada T6G 2H7 iol, Edmonton, AB T6G 2H7, Canada Columbia Univ Coll Phys & Surg, Dept Med, New York, NY 10032 USA Columbia Univ Coll Phys & Surg New York NY USA 10032 w York, NY 10032 USA Univ Calif San Francisco, Dept Surg, San Francisco, CA 94143 USA Univ Calif San Francisco San Francisco CA USA 94143 ancisco, CA 94143 USA Univ Calif San Francisco, Dept Med, San Francisco, CA 94143 USA Univ CalifSan Francisco San Francisco CA USA 94143 ancisco, CA 94143 USA Univ Calif San Francisco, Dept Physiol, San Francisco, CA 94143 USA Univ Calif San Francisco San Francisco CA USA 94143 ancisco, CA 94143 USA Texas A&M Univ, Dept Med Biochem, College Stn, TX 77843 USA Texas A&M Univ College Stn TX USA 77843 iochem, College Stn, TX 77843 USA
Titolo Testata:
JOURNAL OF BIOLOGICAL CHEMISTRY
fascicolo: 1, volume: 276, anno: 2001,
pagine: 541 - 550
SICI:
0021-9258(20010105)276:1<541:CIOABW>2.0.ZU;2-O
Fonte:
ISI
Lingua:
ENG
Soggetto:
TRIGLYCERIDE TRANSFER PROTEIN; APOLIPOPROTEIN-B; ENDOPLASMIC-RETICULUM; SECRETORY PROTEINS; HEPG2 CELLS; INTRACELLULAR DEGRADATION; NASCENT POLYPEPTIDES; MOLECULAR CHAPERONES; MEMBRANE-PROTEIN; PAUSE TRANSFER;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Life Sciences
Citazioni:
56
Recensione:
Indirizzi per estratti:
Indirizzo: Fisher, EA CUNY Mt Sinai Sch Med, Cardiovasc Inst, 1 Gustave Levy Pl,POB 1269, New York, NY 10029 USA CUNY Mt Sinai Sch Med 1 Gustave Levy Pl,POB 1269 New York NY USA 10029
Citazione:
R. Pariyarath et al., "Co-translational interactions of apoprotein B with the ribosome and translocon during lipoprotein assembly or targeting to the proteasome", J BIOL CHEM, 276(1), 2001, pp. 541-550

Abstract

Hepatic lipoprotein assembly and secretion can be regulated by proteasomaldegradation of newly synthesized apoB, especially if lipid synthesis or lipid transfer is low. Our previous studies in HepG2 cells showed that, underthese conditions, newly synthesized apoB remains stably associated with the endoplasmic reticulum (ER) membrane (Mitchell, D. M., Zhou, M., Pariyarath, R., Wang, H., Aitchison, J. D., Ginsberg, T-I. N., and Fisher, E. A (1998) Proc. Natl. Acad. Sci. U.S.A. 95, 14733-14738). We now show that independent of lipid synthesis, apoB chains that appear full-length are, in fact, incompletely translated polypeptides still engaged by the ribosome and associated with the ER translocon. In the presence of active lipid synthesis and transfer, translation and lipoprotein assembly are completed, and the complexes exit the ER. Upon omitting fatty acids from, or adding a microsomal triglyceride transfer protein inhibitor to, culture media to reduce lipid synthesis or transfer, respectively, apoB was degraded while it remained associated with the ER and complexed with cytosolic hsp70 and proteasomes. Thus, unlike other ER substrates of the proteasome, such as major histocompatibility complex class I molecules, apoB does not fully retrotranslocate to the cytosol before entering the ubiquitin-proteasome pathway. Although, uponimmunofluorescence, apoB in proteasome-inhibited cells accumulated in punctate structures similar in appearance to aggresomes (cytosolic structures containing molecules irreversibly lost from the secretory pathway), these apoB molecules could be secreted when lipid synthesis was stimulated. The results suggest a model in which 1) apoB translation does not complete until lipoprotein assembly terminates, and 2) assembly with lipids or entry into the ubiquitin-proteasome pathway occurs while apoB polypeptides remain associated with the translocon and attached to the ribosome.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 09/07/20 alle ore 13:27:46