Amino-terminal deletion of heparin-binding epidermal growth factor-like growth factor4-127 stimulates cell proliferation but lacks insulin-like activity.
Heparin-binding epidermal growth factor-like growth factor (HB-EGF) Northern analysis demonstrated a novel 0.8-kb liver-specific HB-EGF transcript in addition to the endogenous 2.5-kb HB-EGF full-length transcript present in kidney, lung and liver tissues. Reverse transcriptase-polymerase chain reaction screening of liver RNA suggests that the 0.8-kb HB-EGF transcript lacks at least a portion of the amino-terminal EGF-like domain. In light of these data, we have constructed a human HB-EGF cDNA (HB-EGF(DeltaN)) which lacks 373 bp, encoding the majority of the extracellular EGF-like domain, while maintaining the ectodomain 'shedding' site, transmembrane and cytoplasmic domains.


OBJECTIVE
The goal of this study is to characterize the ability of HB-EGF(DeltaN) to (i) stimulate cell proliferation and (ii) determine whether down-regulation of insulin-like growth factor-binding protein (IGFBP)-3 and -4 mRNA is regulated by soluble, mature HB-EGF or HB-EGF C.


METHODS
HB-EGF(DeltaN) encodes nucleotides +1-10 of exon 1 linked to nucleotides 383-627 of the carboxy-terminal portion of exon 3 through exon 5.


RESULTS
Expression of HB-EGF(DeltaN) in mouse fibroblasts (MLC) resulted in 6.5- and 8-kDa HB-EGF immunoreactive proteins, stimulated tyrosine phosphorylation of p42 kDa and cell proliferation in MLC, but lacked the ability to bind EGF receptors. Finally, HB-EGF(DeltaN) failed to down-regulate IGFBP-3 and -4 mRNA when expressed in normal rat kidney cells.


CONCLUSIONS
These findings demonstrate that amino-terminally truncated, membrane-bound form of HB-EGF stimulates cell proliferation but lacks insulin-like signalling, suggesting that insulin-like signalling is mediated by soluble, mature HB-EGF binding to EGF receptors.
Zhou
Z
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Department of Zoology, Miami University, Oxford, OH 45056, USA.
Harding
P A
PA
D017398:Alternative Splicing; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001667:Binding, Competitive; D002460:Cell Line; D049109:Cell Proliferation; D018076:DNA, Complementary / Q000737:chemistry / Q000235:genetics; D004815:Epidermal Growth Factor / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D066246:ErbB Receptors / Q000378:metabolism; D020869:Gene Expression Profiling; D066257:Heparin-binding EGF-like Growth Factor; D006801:Humans; D007328:Insulin / Q000378:metabolism*; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000235:genetics / Q000378:metabolism; D036341:Intercellular Signaling Peptides and Proteins; D051379:Mice; D008969:Molecular Sequence Data; D010750:Phosphoproteins / Q000378:metabolism; D011498:Protein Precursors / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051381:Rats; D017384:Sequence Deletion
D018076:DNA, Complementary; C587883:HBEGF protein, human; C587884:Hbegf protein, mouse; C587885:Hbegf protein, rat; D066257:Heparin-binding EGF-like Growth Factor; D007328:Insulin; D018972:Insulin-Like Growth Factor Binding Protein 3; D036341:Intercellular Signaling Peptides and Proteins; D010750:Phosphoproteins; D011498:Protein Precursors; D012333:RNA, Messenger; D004815:Epidermal Growth Factor; D066246:ErbB Receptors