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.
Kelber
J A
JA
Clayton Foundation Laboratories for Peptide Biology, The Salk Institute for Biological Studies, La Jolla, CA 92037, USA.
Panopoulos
A D
AD
Shani
G
G
Booker
E C
EC
Belmonte
J C
JC
Vale
W W
WW
Gray
P C
PC
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