Identification and biological characterization of an epidermal growth factor-related protein: cripto-1.
The human and mouse cripto-1 (CR-1) genes can code for proteins related in structure to epidermal growth factor (EGF). A specific 36-kDa immunoreactive protein was detected by Western blot analysis in human cell lines that express CR-1 mRNA but not in cell lines that fail to express this transcript. Immunoprecipitation of GEO colon carcinoma or mouse embryonal carcinoma cells detected 27-29-kDa and 24-kDa proteins, respectively. Cell lysates and conditioned medium that were prepared from several CHO clones and were expressing either a recombinant human or mouse CR-1 cDNA contained immunospecific 27-29-kDa and 24-kDa proteins, respectively. Monensin or tunicamycin treatment resulted in a shift of the 27-29-kDa human CR-1 protein to 24 kDa and 20 kDa, respectively. The 20-kDa protein was also observed after digestion of the 27-29-kDa human CR-1 protein with N-glycosidase F. Using two CR-1 synthetic refolded peptides that correspond to the EGF-like domain of the human CR-1 sequence or conditioned medium obtained from human CR-1 expressing CHO cells, growth stimulatory activity could be detected on non-transformed human mammary epithelial cells and on two human breast cancer cell lines. EGF receptor-blocking antibody did not inhibit the growth stimulatory action of the CR-1 protein. Likewise, the CR-1 refolded peptides or conditioned medium from the human CR-1-expressing CHO cells failed to inhibit the binding of 125I-EGF in an EGF-radioreceptor assay. These data demonstrate that the CR-1 is a glycoprotein that can function as a growth factor through an EGF receptor-independent pathway.
Brandt
R
R
Tumor Growth Factor Section, Laboratory of Tumor Immunology and Biology, NCI, National Institutes of Health, Bethesda, Maryland 20892.
Normanno
N
N
Gullick
W J
WJ
Lin
J H
JH
Harkins
R
R
Schneider
D
D
Jones
B W
BW
Ciardiello
F
F
Persico
M G
MG
Armenante
F
F
D000595:Amino Acid Sequence; D000818:Animals; D015153:Blotting, Western; D016466:CHO Cells; D002455:Cell Division; D003001:Cloning, Molecular; D006224:Cricetinae; D018076:DNA, Complementary / Q000235:genetics; D004815:Epidermal Growth Factor; D058851:GPI-Linked Proteins; D015870:Gene Expression; D006133:Growth Substances; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins; D008562:Membrane Glycoproteins; D051379:Mice; D008969:Molecular Sequence Data; D008970:Molecular Weight; D009363:Neoplasm Proteins / Q000737:chemistry*; D010455:Peptides / Q000737:chemistry; D011233:Precipitin Tests; D012333:RNA, Messenger / Q000235:genetics; D011869:Radioligand Assay; D011994:Recombinant Proteins
D018076:DNA, Complementary; D058851:GPI-Linked Proteins; D006133:Growth Substances; D036341:Intercellular Signaling Peptides and Proteins; D008562:Membrane Glycoproteins; D009363:Neoplasm Proteins; D010455:Peptides; D012333:RNA, Messenger; D011994:Recombinant Proteins; C070636:TDGF1 protein, human; C489450:Tdgf1 protein, mouse; D004815:Epidermal Growth Factor