Eukaryotic Cell doi:10.1128/EC.00361-07
Copyright (c) 2007, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.
Target of Rapamycin and LST8 proteins associate with membranes from the endoplasmic reticulum in the unicellular green alga Chlamydomonas reinhardtii
Sandra Díaz-Troya,
Francisco J. Florencio,
and
José L. Crespo*
Instituto de Bioquímica Vegetal y Fotosíntesis, Consejo Superior de Investigaciones Científicas and Universidad de Sevilla; Centro de Investigaciones Científicas Isla de la Cartuja, 41092 Seville, Spain
* To whom correspondence should be addressed. Email:
crespo{at}ibvf.csic.es.
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Abstract |
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The highly conserved target of rapamycin (TOR) kinase is a central controller of cell growth in all eukaryotes. TOR exists in two functionally and structurally distinct complexes, termed TOR complex 1 (TORC1) and TOR complex 2 (TORC2). LST8 is a TOR-interacting protein that is present in both TORC1 and TORC2. Here we report the identification and characterization of TOR and LST8 in large protein complexes in the model photosynthetic green alga Chlamydomonas reinhardtii. We demonstrate that Chlamydomonas LST8 is part of a rapamycin-sensitive TOR complex in this green alga. Biochemical fractionation and indirect immunofluorescence microscopy studies indicate that TOR and LST8 exist in high molecular mass complexes that associate with microsomal membranes and are particularly abundant in the peri-basal body region in Chlamydomonas cells. A Saccharomyces cerevisiae complementation assay demonstrates that Chlamydomonas LST8 is able to functionally and structurally replace endogenous yeast LST8 and allows us to propose that binding of LST8 to TOR is essential for cell growth.
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