The transforming growth factor beta (TGF-beta) family of growth factors control the development and homeostasis of most tissues in metazoan organisms. Work over the past few years has led to the elucidation of a TGF-beta signal transduction network. This network involves receptor serine/threonine kinases at the cell surface and their substrates, the SMAD proteins, which move into the nucleus, where they activate target gene transcription in association with DNA-binding partners. Distinct repertoires of receptors, SMAD proteins, and DNA-binding partners seemingly underlie, in a cell-specific manner, the multifunctional nature of TGF-beta and related factors. Mutations in these pathways are the cause of various forms of human cancer and developmental disorders.

TGF-beta signal transduction.

The recent identification of the SMAD family of signal transducer proteins has unravelled the mechanisms by which transforming growth factor-beta (TGF-beta) signals from the cell membrane to the nucleus. Pathway-restricted SMADs are phosphorylated by specific cell-surface receptors that have serine/threonine kinase activity, then they oligomerize with the common mediator Smad4 and translocate to the nucleus where they direct transcription to effect the cell's response to TGF-beta. Inhibitory SMADs have been identified that block the activation of these pathway-restricted SMADs.

TGF-beta signalling from cell membrane to nucleus through SMAD proteins

The heparan sulfate on the surface of all adherent cells modulates the actions of a large number of extracellular ligands. Members of both cell surface heparan sulfate proteoglycan families, the transmembrane syndecans and the glycosylphosphoinositide-linked glypicans, bind these ligands and enhance formation of their receptor-signaling complexes. These heparan sulfate proteoglycans also immobilize and regulate the turnover of ligands that act at the cell surface. The extracellular domains of these proteoglycans can be shed from the cell surface, generating soluble heparan sulfate proteoglycans that can inhibit interactions at the cell surface. Recent analyses of genetic defects in Drosophila melanogaster, mice, and humans confirm most of these activities in vivo and identify additional processes that involve cell surface heparan sulfate proteoglycans. This chapter focuses on the mechanisms underlying these activities and on the cellular functions that they regulate.

Functions of Cell Surface Heparan Sulfate Proteoglycans

/pdf/bone-morphogenetic-proteins-multifunctional-regulators-of-2uv2zp3r0o.pdf

Bone morphogenetic proteins: multifunctional regulators of vertebrate development.

Agents that increase the permeability of the outer membrane.

Activin, a member of the transforming growth factor beta protein family, was originally isolated from gonadal fluids and stimulates the release of pituitary follicle-stimulating hormone (FSH). Activin has numerous functions in both normal and neoplastic cells. Various cells synthesize activin and have a specific binding site for this peptide. However, the molecular basis for its actions is unknown. A binding protein for activin was purified from rat ovary and was identical to follistatin, a specific inhibitor of FSH release. It is likely that the binding protein participates in the diverse regulatory actions of activin.

https://science.sciencemag.org/content/sci/247/4944/836.full.pdf

Activin-binding protein from rat ovary is follistatin

Oligosaccharide specificity of galectins: a search by frontal affinity chromatography.

It is unclear whether organ-specific autoantigens are critical for the development of primary Sjogren's syndrome (SS). A 120-kilodalton organ-specific autoantigen was purified from salivary gland tissues of an NFS/sld mouse model of human SS. The amino-terminal residues were identical to those of the human cytoskeletal protein alpha-fodrin. The purified antigen induced proliferative T cell responses and production of interleukin-2 and interferon-gamma in vitro. Neonatal immunization with the 120-kilodalton antigen prevented the disease in mice. Sera from patients with SS reacted positively with purified antigen and recombinant human alpha-fodrin protein, whereas those from patients with systemic lupus erythematosus and rheumatoid arthritis did not. Thus, the immune response to 120-kilodalton alpha-fodrin could be important in the initial development of primary SS.

https://science.sciencemag.org/content/sci/276/5312/604.full.pdf

Identification of α-Fodrin as a Candidate Autoantigen in Primary Sjögren's Syndrome

Galectin-9 (Gal-9) induced the apoptosis of not only T cell lines but also of other types of cell lines in a dose- and time-dependent manner. The apoptosis was suppressed by lactose, but not by sucrose, indicating that β-galactoside binding is essential for Gal-9-induced apoptosis. Moreover, Gal-9 required at least 60 min of Gal-9 binding and possibly de novo protein synthesis to mediate the apoptosis. We also assessed the apoptosis of peripheral blood T cells by Gal-9. Apoptosis was induced in both activated CD4 + and CD8 + T cells, but the former were more susceptible than the latter. A pan-caspase inhibitor (Z-VAD-FMK) inhibited Gal-9-induced apoptosis. Furthermore, a caspase-1 inhibitor (Z-YVAD-FMK), but not others such as Z-IETD-FMK (caspase-8 inhibitor), Z-LEHD-FMK (caspase-9 inhibitor), and Z-AEVD-FMK (caspase-10 inhibitor), inhibited Gal-9-induced apoptosis. We also found that a calpain inhibitor (Z-LLY-FMK) suppresses Gal-9-induced apoptosis, that Gal-9 induces calcium (Ca 2+ ) influx, and that either the intracellular Ca 2+ chelator BAPTA-AM or an inositol trisphosphate inhibitor 2-aminoethoxydiphenyl borate inhibits Gal-9-induced apoptosis. These results suggest that Gal-9 induces apoptosis via the Ca 2+ -calpain-caspase-1 pathway, and that Gal-9 plays a role in immunomodulation of T cell-mediated immune responses.

/pdf/galectin-9-induces-apoptosis-through-the-calcium-calpain-41vjv88ls5.pdf

Galectin-9 Induces Apoptosis Through the Calcium-Calpain-Caspase-1 Pathway

A binding protein for activin was purified from bovine pituitary by affinity chromatography on dextran sulfate- Sepharose CL-4B and activin-Affi-Gel 10. A 52,700-fold purification over the starting crude homogenate was achieved. The purified preparation showed two bands of 36 and 33 kilodalton in sodium dodecyl sulfate-polyacrylamide gel electrophoresis under nonreducing conditions. The ability of each form of the protein to specifically bind activin was determined by ligand blot analysis and binding competition study. Each protein was found to have the same NH2-terminus and its sequence was identical to that of follistatin, which is a specific inhibitor of FSH release. Moreover, the binding protein was shown to inhibit the spontaneous FSH release from cultured pituitary cells as does follistatin. These properties are the same as activin-binding protein that we have obtained from rat ovary. These results support a conclusion that activin-binding protein/follistatin exists also in the pituitary. Activin-bi...

Takanori Nakamura

Papers

Activin-binding protein from rat ovary is follistatin

Oligosaccharide specificity of galectins: a search by frontal affinity chromatography.

Identification of α-Fodrin as a Candidate Autoantigen in Primary Sjögren's Syndrome

Galectin-9 Induces Apoptosis Through the Calcium-Calpain-Caspase-1 Pathway

Activin-binding protein is present in pituitary.