Mitochondria chaperone GRP75 moonlighting as a cell cycle controller to derail endocytosis provides an opportunity for nanomicrosphere intracellular delivery
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Zhihui Gao1,*, Xiuran Niu1,*, Qing Zhang2,*, Hang Chen1, Aiai Gao1, Shanshan Qi1, Rong Xiang1, Mattias Belting3 and Sihe Zhang1
1Department of Biochemistry & Cell Biology, School of Medicine, Nankai University, Tianjin, China
2Department of Clinical Laboratory, Cancer Hospital of Tianjin Medical University, Tianjin, China
3Department of Clinical Sciences, Section of Oncology, Lund University, Lund, Sweden
*These authors have contributed equally to this work
Sihe Zhang, email: email@example.com
Keywords: GRP75, cell cycle, clathrin-mediated endocytosis, clathrin-independent endocytosis, nanomicrosphere
Received: February 06, 2017 Accepted: March 27, 2017 Published: April 19, 2017
Understanding how cancer cells regulate endocytosis during the cell cycle could lead us to capitalize this event pharmacologically. Although certain endocytosis pathways are attenuated during mitosis, the endocytosis shift and regulation during the cell cycle have not been well clarified. The conventional concept of glucose-regulated proteins (GRPs) as protein folding chaperones was updated by discoveries that translocated GRPs assume moonlighting functions that modify the immune response, regulate viral release, and control intracellular trafficking. In this study, GRP75, a mitochondria matrix chaperone, was discovered to be highly expressed in mitotic cancer cells. Using synchronized cell models and the GRP75 gene knockdown and ectopic overexpression strategy, we showed that: (1) clathrin-mediated endocytosis (CME) was inhibited whereas clathrin-independent endocytosis (CIE) was unchanged or even up-regulated in the cell cycle M-phase; (2) GRP75 inhibited CME but promoted CIE in the M-phase, which is largely due to its high expression in cancer cell mitochondria; (3) GRP75 targeting by its small molecular inhibitor MKT-077 enhanced cell cycle G1 phase-privileged CME, which provides an opportunity for intracellular delivery of nanomicrospheres sized from 40 nm to 100 nm. Together, our results revealed that GRP75 moonlights as a cell cycle controller and endocytosis regulator in cancer cells, and thus has potential as a novel interference target for nanoparticle drugs delivery into dormant cancer cells.
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