A mitogenic peptide amide encoded within the E peptide domain of the insulin-like growth factor IB prohormone.

Abstract

We have identified an amino acid sequence within the E peptide of the insulin-like growth factor IB (IGF-IB) precursor that is biologically active and designated this peptide insulin-like growth factor IB-(103-124) E1 amide (IBEl). Its existence was predicted by a flanking Gly-Lys-LysLys, a signal sequence for sequential proteolytic cleavage and peptidyl C-terminal amidation. A synthetic analog of the predicted IBE, peptide, designated Y-23-R-NH2, was generated with tyrosine added at position 0. This peptide at 2-20 nM had growth-promoting effects on both normal and malignant human bronchial epithelial cells. Y-23-R-NH2 bound to specific high-affinity receptors (Kd = 2.8 ± 1.4 x 10-11 M) present at 1-2 x 104 binding sites per cell. Ligand binding was not inhibited by recombinant insulin or recombinant IGF-I. Furthermore, a monoclonal antibody antagonist to the IGF-I receptor (aIR3) did not suppress the proliferative response induced by Y-23-R-NH2. In addition, C-terminal amidation was shown to be important in receptor recognition since the free-acid analog of IBE1 (Y-23-R-OH) did not effectively compete for binding and was not a potent agonist of proliferation. Immunoblot analysis of human lung tumor cell line extracts using an antibody raised against Y-23-R-NH2 detected a low molecular mass band of -5 kDa, implying that a protein product is produced that has immunological similarity to IBE1.Extracts of human, mammalian, and avian livers analyzed on an immunoblot with the anti-Y-23-R-NH2 antibody contained proteins of :21 kDa that were specifically recognized by the antiserum and presumably represent an IGF-I precursor molecule. This implies that in species where an IGF-I mRNA with homology to the human IGF-IB E domain has not yet been described, an alternate mRNA must be produced that contains a sequence similar to that of the midportion of the human IGF-IB E domain. Our rmdings demonstrate that IBE1 is a growth factor that mediates its effect through a specific highaffinity receptor and is most likely conserved in many species.

Induction of Apoptosis in Human Cancer Cells by Human Eb- or Rainbow Trout Ea4-Peptide of Pro-Insulin-Like Growth Factor-I (Pro-IGF-I)

“…Recently, Mark Chen in Taiwan also demonstrated that Ea2-peptide of zebrafish exerted a stimulatory effect on incorporation of 35 S-sulfate into zebrafish gill bronchial cartilage in a sulfation assay (personal communication). These results are consistent with those reported in mammals (Siegfried et al, 1992;Matheny et al, 2010;Yang and Goldspink 2002). Further studies conducted in our laboratory showed that both recombinant rtEa4-or synthetic hEbpeptide exerted unexpected anti-cancer cell activities in established human cancer cell lines such as MDA-MB-231, HT-29, HepG2, SK-N-F1, SKOV-3A, PC-3 and OVCAR-3B (Chen et al, , 2007Kuo and Chen 2002).…”

“…Third, different isoforms of pro-IGF-I transcripts are expressed in a tissue-specific and developmental stage-specific manner, and exhibiting differential responses to growth hormone (Shamblott and Chen 1993;Duguay 1994;Yang and Goldspink 2002). Siegfried et al (1992) reported the first evidence that hEbpeptide contained biological activity. In their studies, Siegfried and colleagues showed that a synthetic peptide amide with 23 amino acid residues (Y-23-R-NH 2 ) of the hEb-peptide (a.a. 103-124) at 2-20 nM exerted mitogenic activity in normal and malignant human bronchial epithelial cells.…”

Insulinlike Growth Factor-1Ec (MGF) Expression in Eutopic and Ectopic Endometrium: Characterization of the MGF E-Peptide Actions In Vitro

“…Furthermore, our data documented that a synthetic MGF E-peptide can stimulate the proliferation of human KLE cells, an endometrial carcinoma cell line with a phenotype of endometrial-like cells, via an IGF-1R-independent and IR-independent mechanism. These data suggest that a 4, and it is responsible for binding with the IGF receptors and different E-domain products (Figure 1), which contain different parts of exon 5 and/or exon 6 (8)(9)(10)(11) and have been proposed to act autonomously (8,12).…”

Differential expression of IGF-1 mRNA isoforms in colorectal carcinoma and normal colon tissue

“…It may be responsible for both mitogenic (26) and inhibitory effects on cancer cell growth (27). Furthermore, peptide Eb, which is composed of Eb1 and Eb2 peptides may exert mitogenic effects on IGF-1 independently; however, the activity of both peptides differs in various types of tissue (28). Peptide Ec (MGF) was originally identified in the liver, while higher amounts have been found in muscle following training (29,30).…”