Contact Information


Rm 3059 Duke South Hospital
DUMC 3712
Durham, NC 27710
Email  
(919) 684-3528

Pizzo Lab

Salvatore Pizzo, MD PhD

Pizzo Lab

Salvatore Pizzo, MD, PhD

Distinguished Professor of Pathology

Research Interests

Pizzo modelOur laboratory has historically studied proteinases and their regulation by the plasma proteinase inhibitor α2-macroglobulin (α2M).  When α2M is "activated" (α2M*) by interacting with a proteinase, it binds to cell surface receptors which rapidly remove the complexes from the external environment.  The first receptor characterized was the low density lipoprotein-related receptor (Kd 1-5 mM, ~100,000-200,000 receptors/cell).  LRP is a scavenger receptor which binds and internalizes a number of ligands. Beginning in the 1990's we identified a second, very high affinity receptor (Kd 50-100 pM, 5,000-10,000 receptors/cell).  Unlike LRP, this α2M* receptor is coupled to signal transduction cascades (1).  α2M* binds to the NH2-terminal domain where it activates pro-proliferative, anti-apoptotic, and pro-promigratory signaling (1-6).  This receptor is most prominently found on the surface of malignant, but not normal cells (4-6).  This includes prostate, breast, lung, colon, stomach, lung, and ovarian cancers among others.  It was identified by our laboratory as cell surface-associated GRP78 (4).  This was a surprising observation since all previous studies indicated that GRP78, the lynchpin of the unfolded protein response, occurs only in the ER.  Here it functions to promote proper folding of proteins, particularly in highly stressed cells. Cancer cells, by definition, are highly stressed and express high levels of intra-ER GRP78.  Apparently in such cells a fraction of this protein "leaks" to the cell surface, functioning as a G protein-coupled receptor (1-6). Studies beginning in 2003 demonstrated that auto-antibodies directed against GRP may occur in the serum of patients harboring various malignancies.  The occurrence of these auto-antibodies is a harbinger of a poor prognosis. We demonstrated that these auto-antibodies bind to or near the α2M* binding site and they function as agonists acting like α2M* (7), thus explaining the association with a poor prognosis.  As a cell surface receptor, GRP78 has essentially unique properties.  Both the NH2- and COOH-terminal domains are exposed on the cell surface (8).  Our studies remarkably found that ligation of the COOH-terminal domain triggers signaling cascades that are anti-proliferative, pro-apoptotic, and anti-migratory (9). Such dual functionality is not known for any other receptor.  Importantly, ligation of the COOH-terminal domain, while it does not block binding to the NH2-terminal domain, overrides the pro-proliferative effects of ligating the α2M* binding site (9).  These antibodies, which do not appear in the sera of patients with highly malignant tumors, have significant therapeutic potential.  Interestingly, cell surface GRP78 is associated with stem cell-like tumor cells, which are resistant to chemotherapy and against which there are no specific drugs (10, 11).  We continue to also characterize the α2M* signaling cascade. Extensive recent work demonstrates that α2M* is a more potent regulator of glucose and lipid metabolism than insulin in cancer cells, but not normal cells (12).  The models studied in our laboratory include prostate, brain, ovary, and breast cancer.  Our collaborative interactions with the laboratory of Dr. Robin Bachelder have implicated cell surface GRP78 in cancer stem-like behaviors, including multi-drug resistance (10, 11). 

References

  1. Misra, U.K., Chu, C.T., Gawdi, G., and Pizzo, S.V.:  Evidence for a Second α2-Macroglobulin Receptor. J. Biol. Chem 269: 12541-12547, 1994.
  2. Howard, G.C., Yamaguchi, Y., Misra, U.K., Gawdi, G., Nelsen, A., DeCamp, D.L., and Pizzo, S.V.:   Selective Mutations in Cloned and Expressed α2-Macroglobulin Receptor Binding Fragment Alter Binding to Either the α2-Macroglobulin Signaling Receptor or the Low Density Lipoprotein Receptor-Related Protein/α2-Macroglobulin. J. Biol. Chem 271: 14105-14111, 1996.
  3.  Misra, U.K. and Pizzo, S.V.:  Binding of Receptor-Recognized Forms of α2-Macroglobulin to the α2-Macroglobulin Signaling Receptor Activates Phosphatidylinositol-3 Kinase. J. Biol. Chem, 273: 13399-13402, 1998 (Communication).
  4. Misra, U.K., Gonzalez-Gronow, M., Gawdi, G., Hart, J.P., Johnson, C.E., and Pizzo, S.V.:  The Role of Grp 78 in α2-Macroglobulin-Induced Signal Transduction:  Evidence from RNA Interference that the Low Density Lipoprotein-Receptor Related Protein is Associated with, but Not Necessary for, GRP78-Mediated Signal Transduction.  J. Biol. Chem., 277: 42082-42087, 2002.
  5. Misra, U.K., Deedwani, R., and Pizzo,S.V.:  Binding of Activated α2-Macroglobulin to its Cell Surface Receptor GRP78 in 1-LN Prostate Cancer Cells Regulates PAK-2-Dependent Activation of LIMK.  J. Biol. Chem., 280: 26278-26286, 2005.
  6. Misra, U.K., Deedwania, R., and Pizzo, S.V.:  Activation and Cross Talk Between Akt, NFkB, and Unfolded Protein Response Signaling in 1-LN Prostate Cancer Cells Consequent to Ligation of Cell Surface-Associated GRP78.  J. Biol. Chem., 281: 13694-13707, 2006.
  7. Gonzalez-Gronow, M., Cuchacovich, M., Llanos, C., Urzua,C., Gawdi, G., and Pizzo, S.V.:  Prostate Cancer Cell Proliferation In Vitro is Modulated by Antibodies against Glucose-Regulated Protein 78 Isolated from Patient Serum.  Cancer Res. 66: 11424-11431, 2006.
  8. Ray, R., de Ridder, G.G., Eu, J.P., Paton, A.W., Paton, J.C., and Pizzo, S.V.:  TheEscherichia coli Subtilase Cytotoxin A Subunit Specifically Cleaves Cell-Surface GRP78 and Abolishes COOH-Terminal-Dependent Signaling. J. Biol. Chem. 287: 32755-32769, 2012.
  9. Misra, U.K. and Pizzo, S.V.:  Modulation of the Unfolded Protein Response in Prostate Cancer Cells by Antibody-Directed Against the Carboxyl-terminal Domain of GRP78.  Apoptosis,  15(2): 173-182, 2010. 
  10. Mo, L., Bachelder, R.E., Kennedy, M., Chen, P-H., Chi, J-T., Berchuck, A., Cianciolo, G., and Pizzo, S.V.:  Syngeneic murine ovarian cancer model reveals that ascites enriches for ovarian cancer stem-like cells expressing membrane GRP78.  Molec Cancer Therapeutics, 14(3): 747-756, 2015.
  11. Mo, L., Pospichalova, V., Huang, Z., Murphy, S.K., Payne, S., Wang, F., Kennedy, M., Cianciolo, G., Bryja, V., Pizzo, S.V., Bachelder, R.:  Ascites increases expression/function of Multidrug Resistance Proteins in Ovarian Cancer Cells.  PloS One,  Jul 6; 10(7): e0131579, 2015
  12. Misra, U.K. and Pizzo, S.V.:  Activated a2-macroglobulin binding to human prostate cancer cells triggers insulin-like responses.  J. Biol.Chem., 290(15): 9571-9587, 2015.

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