Cripto is the founding member of the epidermal growth factor-CriptoFRL1Cryptic (EGF-CFC) family of signaling proteins that function in cancer and various developmental processes. These developmental processes include: formation of the germ layers and dorsal organizer, specification of anterior-posterior and left-right axes, and differentiation of heart muscle.1, 2 Other members of the EGF-CFC family include Cryptic, Xenopus FRL-1 and zebrafish OEP (one-eyed pinhead). Overall sequence identity between members of the family is low, but they do share several common domains: a variant EGF-like motif, a novel conserved cysteine-rich domain (called CFC domain), and a C-terminal hydrophobic region. Most EGF-CFC members have a glycosyl-phosphatidylinositol (GPI) anchoring site at the C-terminus and exist as extracellular membrane-anchored proteins. However, naturally-occurring soluble isoforms also exist.
Human Cripto shares 66% and 28% amino acid identity with mouse Cripto and zebrafish OEP, respectively.2 Despite weak conservation in amino acid identity, EGF-CFC family members appear to function similarly in assays for phenotypic rescue of zebrafish oep mutants.2 Both secreted and membrane bound forms of cripto demonstrate biological activity.3
Cripto, also known as CFC-2 or TDGF-1 (teratocarcinoma-derived growth factor), was originally isolated from an undifferentiated human teratocarcinoma cell line as a potential oncogene. It is overexpressed in many types of cancers and acts as a growth factor for tumors.4 Genetic evidence from mice and zebrafish points to a role for cripto as an essential cofactor in Nodal signaling. Cripto and OEP mutants display defects in mesoderm induction and heart morphogenesis, similar to phenotypes seen in Nodal mutants.2 Cripto acts as a cofactor for Nodal by recruiting the Activin type I Receptor, ALK-4, leading to an Act RIIB-ALK4-Cripto-Nodal
complex for signaling.1, 3 Cripto also forms a complex with activin and Act RIIs to block activin signaling.5
Recent work has shown that other TGF-b superfamily members such as Vg1 and GDF-1 also require EGF-CFC cofactors.6 Cripto can also activate mitogen-activated protein kinase (MAPK) and Akt pathways independently of Nodal by directly binding to a membrane-associated
heparan sulfate proteoglycan, glypican-1.7
Source: Human CD33 Signal Peptide (Met 1 -Met 17) Human Cripto-1 (Phe 23-Thr 172) DNA sequence encoding amino acid residues Phe 23-Thr 172 of human Cripto-11 fused at the
amino terminus with the signal peptide from human CD33 (Ciccodicola, A. et al., 1989, EMBO J. 8(7):1987-1991) was expressed in an insect cell line, Sf 21.
Molecular Mass: Based on N-terminal sequencing, the mature recombinant human Cripto-1 preparation contains a mixture of two peptides with Leu 31 and Ser 63 at the N-terminus. The two peptides have calculated molecular masses of 16kD and 13kD. As a result of glycosylation, the recombinant
protein migrates as an approximately 16-20kD protein in SDS-PAGE under reducing conditions.
Purity: > 95%, as determined by SDS-PAGE and visualized by silver stain.
Endotoxin: < 1.0 EU/ug of the protein as determined by the LAL method.
Activity: Measured by its ability to bind human Activin RIB/ALK4 in a functional ELISA. Immobilized rhActivin RIB/Fc at 2ug/ml (100ul/well) will bind rhCripto-1 with a linear range of 0.8-100 ng/ml. This protein will also bind rmNodal in a functional ELISA.
Suitable for use in ELISA. Other applications not tested.
Storage and Stability:
Lyophilized samples are stable for up to twelve months from date of receipt at -20 degrees C to -70 degrees C. Upon reconstitution, this cytokine can be stored under sterile conditions at -20 degrees C to -70 degrees C in a
manual defrost freezer for three months without detectable loss of activity. Avoid repeated freeze-thaw cycles.