title: Sec16B is involved in the endoplasmic reticulum export of the peroxisomal membrane biogenesis factor peroxin 16 (Pex16) in mammalian cells.
abstract: Sec16 plays a key role in the formation of coat protein II vesicles, which mediate protein transport from the endoplasmic reticulum (ER) to the Golgi apparatus. Mammals have two Sec16 isoforms: Sec16A, which is a longer primary ortholog of yeast Sec16, and Sec16B, which is a shorter distant ortholog. Previous studies have shown that Sec16B, as well as Sec16A, defines ER exit sites, where coat protein II vesicles are formed in mammalian cells. Here, we reveal an unexpected role of Sec16B in the biogenesis of mammalian peroxisomes. When overexpressed, Sec16B was targeted to the entire ER, whereas Sec16A was mostly cytosolic. Concomitant with the overexpression of Sec16B, peroxisomal membrane biogenesis factors peroxin 3 (Pex3) and Pex16 were redistributed from peroxisomes to Sec16B-positive ER membranes. Knockdown of Sec16B but not Sec16A by RNAi affected the morphology of peroxisomes, inhibited the transport of Pex16 from the ER to peroxisomes, and suppressed expression of Pex3. These phenotypes were significantly reversed by the expression of RNAi-resistant Sec16B. Together, our results support the view that peroxisomes are formed, at least partly, from the ER and identify a factor responsible for this process.
authors.affiliation: School of Life Sciences, Tokyo University of Pharmacy and Life Sciences, Hachioji, Tokyo 192-0392, Japan.
authors.forename: Shusuke
authors.initials: S
authors.lastname: Yonekawa
authors.forename: Akiko
authors.initials: A
authors.lastname: Furuno
authors.forename: Takashi
authors.initials: T
authors.lastname: Baba
authors.forename: Yukio
authors.initials: Y
authors.lastname: Fujiki
authors.forename: Yuta
authors.initials: Y
authors.lastname: Ogasawara
authors.forename: Akitsugu
authors.initials: A
authors.lastname: Yamamoto
authors.forename: Mitsuo
authors.initials: M
authors.lastname: Tagaya
authors.forename: Katsuko
authors.initials: K
authors.lastname: Tani
mesh_terms: D001665:Binding Sites / Q000235:genetics; D015153:Blotting, Western; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D006056:Golgi Apparatus / Q000378:metabolism; D057809:HEK293 Cells; D006367:HeLa Cells; D006801:Humans; D008164:Luminescent Proteins / Q000235:genetics / Q000378:metabolism; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D008856:Microscopy, Fluorescence; D020675:Peroxisomes / Q000378:metabolism; D011485:Protein Binding; D021381:Protein Transport; D034622:RNA Interference; D014162:Transfection; D033921:Vesicular Transport Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D004268:DNA-Binding Proteins; D008164:Luminescent Proteins; D008565:Membrane Proteins; C486345:PEX16 protein, human; C517555:SEC16A protein, human; C443860:SEC16B protein, human; C507455:SEC31A protein, human; D033921:Vesicular Transport Proteins