Cloning and Sequence Analysis of the Human MG160, a Fibroblast Growth Factor and E-Selectin Binding Membrane Sialoglycoprotein of the Golgi Apparatus

Abstract

The amino acid sequence of MG160, a membrane sialoglycoprotein of the medial cisternae of the rat Golgi apparatus, is more than 90% identical with CFR, a fibroblast growth factor (FGF) binding protein of chicken membranes, and with ESL-1, a ligand for E-selectin of plasma membranes of myeloid cells; furthermore, MG160, isolated by immunoaffinity chromatography from rat brain membranes, binds to basic FGF. The gene for MG160 has been assigned to human chromosome 16q22-23. To characterize this protein further in the human, its cDNA was cloned and sequenced. The protein has a large luminal domain composed of an initial proline-glutamine-rich segment, encoded by an uninterrupted exonic sequence of several CAG-CAA repeats. Expansion of CAG repeats has been implicated in the etiology of several neurodegenerative diseases. The proline-glutamine-rich segment is followed by 16 cysteine-rich repeats that contain five potential asparagine-linked glycosylation sites, which are conserved in the human, rat, mouse, and chicken. The large intralumenal domain of the protein is followed by a single transmembrane domain and a 13-amino-acid cytoplasmic carboxy-terminal tail, which is identical to that in the chicken, rat, and mouse. The overall amino acid identifies between MG160, CFR, and ESL-1 range from 88% to 95%. In several human fetal and adult tissues, three mRNA transcripts for MG160 of 10 kb, 5 kb, and 3.8 kb were identified by Northern blot analysis of poly(A)-selected mRNAs. These transcripts may represent alternatively spliced mRNAs of the protein or mRNAs encoding closely related proteins of the Golgi apparatus and/or plasma membranes.

Identification and characterization of an intracellular protein complex that binds fibroblast growth factor-2 in bovine brain

“…Quantitative electron microscopy and immunocytochemical analysis of p79ER-expressing rat fibroblasts (FR3T3-316) confirmed the localization of p79ER in structures morphologically indistinguishable from those labelled for the ER membrane protein marker calnexin. This revealed that more than 75 % of anti-p79 gold labelling was located in the ER compartment and almost 15 % was located in the Golgi apparatus, where MG-160-like proteins are mainly localized [15,18,35]. These data could suggest a rapid recycling of p79ER between the ER and the Golgi, with an accumulation of p79 in the ER, as previously described for other proteins [36,37].…”

“…Previously, only CFR and MG-160 have been shown to bind FGF-2 [11,15]. Zhou et al [39] have shown that CFR possibly harbours two distinct FGF-binding sites ; one of these is heparin-dependent, whereas the other is not.…”

“…The N-terminal amino acid sequences of p79 and p46 were determined, as well two p79 and one p46 internal peptide sequences ( Figures 2B and 2C). The p150 sequences were highly similar to the CFR-like proteins [11], MG-160 [14,15] or ESL-1 [16]. The p79 sequences were very similar to those of GBP [19] or p79M [20], and the p46 sequences were identical to that of p46M [20].…”

“…No immunoreactive MG-160 or p46 was detectable in peak 1, although a small amount of a 70-75 kDa species was detected by anti-p79 antibodies (results not shown). FGF-2 was shown previously to bind CFR and MG-160 [10,15]. To elucidate the interactions between FGF-2 and p79, rbFGF-2 and N-tagged p79 were incubated in the presence of 3 mM dithiothreitol, 5 mM CaCl # , 5 mM ATP or 5 mM EDTA.…”

A Novel Proliferation-Associated Variant of CFR-1 Defined by a Human Monoclonal Antibody

“…In Chinese hamster ovary cells (CHO), CFR-1 was found to be expressed only in the Golgi apparatus (Burrus et al, 1992), but it can also be secreted in a mutated form (Zuber et al, 1997). Depending on the organism, two detected variants of CFR-1, ESL-1 and MG-160, share sequence homologies between 88% and 95% (Burrus et al, 1992;Mourelatos et al, 1996;Steegmaier et al, 1995;Stieber et al, 1995) and do not appear to share any sequence homologies to other known proteins. Function and cellular distribution of CFR-1 and the homologues is relatively unknown and contradictory.…”