ABSTRACT
Ciliary neurotrophic factor (CNTF) is a cytokine supporting the differentiation and survival of various cell types in the peripheral and central nervous systems. Its receptor complex consists of a non-signaling alpha chain, CNTFR, and two signaling beta chains, gp130 and the leukemia inhibitory factor receptor (LIFR). Striking phenotypic differences between CNTF- and CNTFR-deficient mice suggest that CNTFR serves as a receptor for a second, developmentally important ligand. We have identified this factor as a stable secreted complex of cardiotrophin-like cytokine (CLC) and the soluble receptor cytokine-like factor-1 (CLF). CLF expression was required for CLC secretion, and the complex acted only on cells expressing functional CNTF receptors. The CLF/CLC complex activated gp130, LIFR and signal transducer and activator of transcription 3 (STAT3) and supported motor neuron survival. Our results indicate that the CLF/CLC complex is a second ligand for CNTFR with potentially important implications in nervous system development.
Subject(s)
Cytokines/metabolism , Receptor, Ciliary Neurotrophic Factor/metabolism , Receptors, Cytokine/metabolism , Animals , COS Cells , Cell Differentiation/physiology , Cell Survival/physiology , Ligands , Motor Neurons/cytology , Motor Neurons/metabolism , Nerve Degeneration/physiopathology , Radioligand Assay , Tumor Cells, CulturedABSTRACT
A cDNA encoding a novel human matrix metalloproteinase (MMP), named MMP-26, was cloned from fetal cDNA. The deduced 261-amino-acid sequence is homologous to macrophage metalloelastase (51.8% identity). It includes only the minimal characteristic features of the MMP family: a signal peptide, a prodomain and a catalytic domain. As with MMP-7, this new MMP does not comprise the hemopexin domain, which is believed to be involved in substrate recognition. A study of MMP-26 mRNA steady states levels reveals, among the tissue examined, a specific expression in placenta. MMP-26 mRNA could also be detected in several human cell lines such as HEK 293 kidney cells and HFB1 lymphoma cells. Recombinant MMP-26 was produced in mammalian cells and used to demonstrate a proteolytic activity of the enzyme on gelatin and beta-casein.
Subject(s)
Matrix Metalloproteinases/genetics , Placenta/enzymology , Pregnancy Proteins/genetics , Amino Acid Sequence , Animals , COS Cells , Catalytic Domain , Cell Line , Chlorocebus aethiops , DNA, Complementary/genetics , Expressed Sequence Tags , Gene Expression Profiling , Humans , Matrix Metalloproteinases/metabolism , Matrix Metalloproteinases, Secreted , Molecular Sequence Data , Organ Specificity , Protein Sorting Signals/genetics , Protein Structure, Tertiary , RNA, Messenger/metabolism , Recombinant Fusion Proteins/metabolism , Sequence Homology, Amino Acid , Substrate Specificity , TransfectionABSTRACT
Using the sequence of cosmids derived from chromosome 19p12, we have identified a gene encoding a novel protein, BSMAP (brain-specific membrane-anchored protein) and cloned cDNA encoding the full-length open reading frame. Northern blot analysis revealed that BSMAP mRNA is preferentially expressed at a high level in the brain. BSMAP has a putative transmembrane domain and is predicted to be a type-I membrane glycoprotein. Genomic sequence analysis revealed that the gene encoding BSMAP consists of eight exons spanning approximately 8 kb and lies 6 kb away from the gene encoding CLF-1 in a reverse orientation. Although no candidate genetic disorders were found to map either to this precise region of chromosome 19 or to the syntenic region of the mouse genome, the highly specific expression of BSMAP mRNA suggests a role for the protein in CNS function.
