Farré Jean-Claude, Carolino Krypton, Stasyk Oleh V, Stasyk Olena G, Hodzic Zlatan, Agrawal Gaurav, Till Andreas, Proietto Marco, Cregg James, Sibirny Andriy A, Subramani Suresh
Section of Molecular Biology, Division of Biological Sciences, University of California, San Diego, La Jolla, CA 92093, USA.
Institute of Cell Biology, National Academy of Sciences of Ukraine, Drahomanov Street 14/16, Lviv 79005, Ukraine.
J Mol Biol. 2017 Nov 24;429(23):3743-3762. doi: 10.1016/j.jmb.2017.10.009. Epub 2017 Oct 14.
Peroxisomal membrane proteins (PMPs) traffic to peroxisomes by two mechanisms: direct insertion from the cytosol into the peroxisomal membrane and indirect trafficking to peroxisomes via the endoplasmic reticulum (ER). In mammals and yeast, several PMPs traffic via the ER in a Pex3- and Pex19-dependent manner. In Komagataella phaffii (formerly called Pichia pastoris) specifically, the indirect traffic of Pex2, but not of Pex11 or Pex17, depends on Pex3, but all PMPs tested for indirect trafficking require Pex19. In mammals, the indirect traffic of PMPs also requires PEX16, a protein that is absent in most yeast species. In this study, we isolated PEX36, a new gene in K. phaffii, which encodes a PMP. Pex36 is required for cell growth in conditions that require peroxisomes for the metabolism of certain carbon sources. This growth defect in cells lacking Pex36 can be rescued by the expression of human PEX16, Saccharomyces cerevisiae Pex34, or by overexpression of the endogenous K. phaffii Pex25. Pex36 is not an essential protein for peroxisome proliferation, but in the absence of the functionally redundant protein, Pex25, it becomes essential and less than 20% of these cells show import-incompetent, peroxisome-like structures (peroxisome remnants). In the absence of both proteins, peroxisome biogenesis and the intra-ER sorting of Pex2 and Pex11C are seriously impaired, likely by affecting Pex3 and Pex19 function.
过氧化物酶体膜蛋白（PMPs）通过两种机制转运至过氧化物酶体：从细胞质直接插入过氧化物酶体膜以及通过内质网（ER）间接转运至过氧化物酶体。在哺乳动物和酵母中，几种PMPs以依赖Pex3和Pex19的方式通过内质网转运。具体而言，在毕赤酵母（以前称为巴斯德毕赤酵母）中，Pex2的间接转运依赖于Pex3，但Pex11或Pex17则不然，不过所有测试过间接转运的PMPs都需要Pex19。在哺乳动物中，PMPs的间接转运还需要PEX16，而大多数酵母物种中不存在这种蛋白质。在本研究中，我们分离出了毕赤酵母中的一个新基因PEX36，它编码一种PMP。在某些碳源代谢需要过氧化物酶体的条件下，细胞生长需要Pex36。缺乏Pex36的细胞中的这种生长缺陷可以通过人PEX16、酿酒酵母Pex34的表达或内源性毕赤酵母Pex25的过表达来挽救。Pex36对于过氧化物酶体增殖不是必需蛋白，但在缺乏功能冗余蛋白Pex25的情况下，它变得必不可少，并且这些细胞中不到20%显示出导入功能缺陷的过氧化物酶体样结构（过氧化物酶体残余物）。在两种蛋白质都不存在的情况下，过氧化物酶体生物发生以及Pex2和Pex11C在内质网中的分选会受到严重损害，可能是通过影响Pex3和Pex19的功能。
