Blockade of Cripto binding to cell surface GRP78 inhibits oncogenic Cripto signaling via MAPK/PI3K and Smad2/3 pathways.
Cripto is a developmental oncoprotein that signals via mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinase (ERK), phosphatidylinositol 3-kinase (PI3K)/Akt and Smad2/3 pathways. However, the molecular basis for Cripto coupling to these pathways during embryogenesis and tumorigenesis is not fully understood. In this regard, we recently demonstrated that Cripto forms a cell surface complex with the HSP70 family member glucose-regulated protein-78 (GRP78). Here, we provide novel functional evidence demonstrating that cell surface GRP78 is a necessary mediator of Cripto signaling in human tumor, mammary epithelial and embryonic stem cells. We show that targeted disruption of the cell surface Cripto/GRP78 complex using shRNAs or GRP78 immunoneutralization precludes Cripto activation of MAPK/PI3K pathways and modulation of activin-A, activin-B, Nodal and transforming growth factor-beta1 signaling. We further demonstrate that blockade of Cripto binding to cell surface GRP78 prevents Cripto from increasing cellular proliferation, downregulating E-Cadherin, decreasing cell adhesion and promoting pro-proliferative responses to activin-A and Nodal. Thus, disrupting the Cripto/GRP78 binding interface blocks oncogenic Cripto signaling and may have important therapeutic value in the treatment of cancer.
Clayton Foundation Laboratories for Peptide Biology, The Salk Institute for Biological Studies, La Jolla, CA 92037, USA.
J A
JA
Kelber
A D
AD
Panopoulos
G
G
Shani
E C
EC
Booker
J C
JC
Belmonte
W W
WW
Vale
P C
PC
Gray
D028341:Activins / Q000494:pharmacology; D000906:Antibodies / Q000494:pharmacology; D015153:Blotting, Western; D015820:Cadherins / Q000378:metabolism; D002448:Cell Adhesion / Q000187:drug effects; D002460:Cell Line; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D000091342:Endoplasmic Reticulum Chaperone BiP; D004815:Epidermal Growth Factor / Q000235:genetics / Q000378:metabolism*; D058851:GPI-Linked Proteins; D006360:Heat-Shock Proteins / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D006801:Humans; D047468:Immunoprecipitation; D036341:Intercellular Signaling Peptides and Proteins; D008156:Luciferases / Q000235:genetics / Q000378:metabolism; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism*; D018613:Microscopy, Confocal; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D008954:Models, Biological; D009363:Neoplasm Proteins / Q000235:genetics / Q000378:metabolism*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D011485:Protein Binding / Q000187:drug effects; D034741:RNA, Small Interfering / Q000235:genetics; D011869:Radioligand Assay; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D051785:Smad Proteins / Q000378:metabolism*; D051899:Smad2 Protein / Q000378:metabolism; D051900:Smad3 Protein / Q000378:metabolism
D028341:Activins; D000906:Antibodies; D015820:Cadherins; D000091342:Endoplasmic Reticulum Chaperone BiP; D004815:Epidermal Growth Factor; D058851:GPI-Linked Proteins; D006360:Heat-Shock Proteins; D036341:Intercellular Signaling Peptides and Proteins; D008156:Luciferases; D008562:Membrane Glycoproteins; D020928:Mitogen-Activated Protein Kinases; D009363:Neoplasm Proteins; D019869:Phosphatidylinositol 3-Kinases; D034741:RNA, Small Interfering; D051785:Smad Proteins; D051899:Smad2 Protein; D051900:Smad3 Protein; C000717247:HSPA5 protein, human; C497782:SMAD2 protein, human; C497790:SMAD3 protein, human; C070636:TDGF1 protein, human; C422405:activin A