Vicki L Mcdonald

The amphiregulin gene encodes a novel epidermal growth factor-related protein with tumor-inhibitory activity

We have isolated the gene for a novel growth regulator, amphiregulin (AR), that is evolutionarily related to epidermal growth factor (EGF) and transforming growth factor alpha (TGF-alpha). AR is a bifunctional growth modulator: it interacts with the EGF/TGF-alpha receptor to promote the growth of normal epithelial cells and inhibits the growth of certain aggressive carcinoma cell lines. The 84-amino-acid mature protein is embedded within a 252-amino-acid transmembrane precursor, an organization similar to that of the TGF-alpha precursor. Human placenta and ovaries were found to express significant amounts of the 1.4-kilobase AR transcript, implicating AR in the regulation of normal cell growth. In addition, the AR gene was localized to chromosomal region 4q13-4q21, a common breakpoint for acute lymphoblastic leukemia.

The interaction of amphiregulin with nuclei and putative nuclear localization sequence binding proteins.

Amphiregulin (AR) is a 23 kDa, bifunctional growth modulating glycoprotein belonging to the epidermal growth factor (EGF) family of polypeptide growth regulators. AR possesses two putative nuclear localization sequences (NLS), binds to DNA sepharose, and localizes to the nucleoli of human ovarian surface epithelial carcinoma cells suggesting that AR has a direct nuclear role. We have found that 125I-labeled AR, when exogenously applied to several carcinoma cell lines, associated with nuclei in a time, temperature, and concentration dependent fashion. The control peptide, EGF, also associated with these fractions but at approximately 20% of the efficiency of AR. Cross-linking experiments with 125I-labeled AR and nuclear fractions derived from various carcinoma and normal cell lines demonstrated that AR binds two proteins of molecular mass 205 and 120 kDa. AR binding to these nuclear fraction proteins was specific and saturable as shown by competition experiments utilizing both SV-40 large T antigen NLS and an AR derived peptide encompassing both putative AR NLS. The combined results suggest that nuclear interactions may play a significant role in AR induced growth responses.

Cleavable CD40Ig fusion proteins and the binding to sgp39

Recombinant immunoglobulin (Ig) fusion proteins of cell surface and intracellular proteins have wide applications. For example, fusion proteins have been used in the isolation, identification and study of ligands and the effects of binding or blocking a receptor-ligand pair, either in vivo or in vitro. For some applications, removal of the immunoglobulin Fc region is advantageous. We have developed two vectors for the expression of Ig fusion proteins that contain recognition sequences for protease cleavage using thrombin. In one vector, the sequence encoding the thrombin cleavage site is located at the junction of the DNA fragment encoding the protein or protein fragment to be studied and the hinge and constant regions of the immunoglobulin, allowing the generation of a monomeric form of the protein of interest. In the second vector, the sequence encoding the thrombin cleavage site is located between the sequences encoding the hinge and constant regions of the immunoglobulin, allowing for the generation of covalent dimers of the recombinant protein without the constant Fc domains. We have used these vectors to produce the constructs encoding two forms of the extracellular domain of CD40, CD40ThrIg and CD40HinThrIg, allowing production of a monomeric and dimeric form of recombinant CD40. Cleavage is efficient and complete. Following cleavage, there was no detectable binding of the monomeric form of CD40 to a soluble form of gp39, the ligand of CD40, while the dimeric form was able to bind. These vectors have been constructed to allow facile substitution with other sequences to generate cleavable forms of other proteins of interest.

Amphiregulin-associated protein: Complete amino acid sequence of a protein produced by the 12-0-tetradecanoylphorbol-13-acetate-treated human breast adenocarcinoma cell line MCF-7

Amphiregulin-associated protein (ARAP) was purified from serum-free conditioned medium of MCF-7, human breast carcinoma cells, treated with 12-0-tetradecanoylphorbol-13-acetate (TPA). ARAP is a single-chain, extremely hydrophilic, heparin-binding protein. Its apparent molecular weight is approximately 21,500 as assessed by gel chromatography and approximately 15,500 as determined by polyacrylamide gel electrophoresis. The complete amino acid sequence of ARAP was determined. The larger form contains 123 amino acids, whereas a shorter form is missing two amino acids at the amino-terminal. ARAP contains 10 cysteines and 30 basic amino acids (23 lysines and 7 arginines). ARP sequence has been found to be identical to protein encoded by human MK gene.