Characterization and Mechanism of Stress-induced Translocation of 78-kilodalton Glucose Regulated Protein (GRP78) to the Cell Surface [Membrane Biology]

February 11th, 2015 by Tsai, Y.-L., Zhang, Y., Tseng, C.-C., Stanciauskas, R., Pinaud, F., Lee, A. S.

GRP78/BiP, a major chaperone in the endoplasmic reticulum (ER), is recently discovered to be preferably expressed on the surface of stressed cancer cells, where it regulates critical oncogenic signaling pathways and is emerging as a target for anti-cancer therapy while sparing normal organs. However, since GRP78 does not contain classical transmembrane domains, its mechanism of transport and its anchoring at the cell surface are poorly understood. Using a combination of biochemical, mutational, FACS and single molecule super-resolution imaging approaches, we discovered that GRP78 majorly exists as a peripheral protein on plasma membrane via interaction with other cell surface proteins including GPI-anchored proteins. Moreover, cell surface GRP78 expression requires its substrate-binding activity but is independent of ATP binding or a membrane insertion motif conserved with HSP70. Unexpectedly, different cancer cell lines rely on different mechanisms for GRP78 cell surface translocation, implying that the process is cell context dependent.
  • Posted in Journal of Biological Chemistry, Publications
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