Biomedical subjects

Ri-Yao Yang

Publications and source records attributed to Ri-Yao Yang.

4 recordsLinked to original sources

PubMed2006

Galectins in apoptosis.

Galectins are a family of animal lectins with affinity for beta-galactosides. By using recombinant proteins, a number of galectins have been shown to interact with cell-surface and extracellular matrix glycoconjugates through lectin-carbohydrate interactions. Through this action, they can affect a variety of cellular processes, and the most extensively documented function is induction of apoptosis. By using gene transfection approaches, galectins have been shown to regulate various cellular processes, including apoptosis. Evidence has been provided that some of these functions involve binding to cytoplasmic and nuclear proteins, through protein-protein interactions, and modulation of intracellular signaling pathways. Thus, some galectins are pro-apoptotic, whereas others are anti-apoptotic; some galectins induce apoptosis by binding to cell surface glycoproteins, whereas others regulate apoptosis through interactions with intracellular proteins. This review describes involvement of galectin-1, -2, -3, -7, -8, -9, and -12 in apoptosis.

Animals↗

PubMed2004

Galectin-12 is required for adipogenic signaling and adipocyte differentiation.

Galectin-12 is a member of the galectin family consisting of beta-galactoside-binding proteins with conserved carbohydrate recognition domains. This protein is preferentially expressed in peripheral blood leukocytes and adipocytes. We previously showed that galectin-12 is induced by cell cycle block at the G(1) phase and causes G(1) arrest when overexpressed (Yang, R.-Y., Hsu, D. K., Yu, L., Ni, J., and Liu, F.-T. (2001) J. Biol. Chem. 276, 20252-20260). Here, we show that the galectin-12 gene is expressed in mouse preadipocytes and is up-regulated when preadipocytes undergo cell cycle arrest, concomitant with acquisition of the competence to undergo differentiation in response to adipogenic hormone stimulation. Following a brief down-regulation 1 day after adipogenic treatment, its expression was once again markedly elevated when cells underwent terminal differentiation. Down-regulation of endogenous galectin-12 expression by RNA interference greatly reduced the expression of the adipogenic transcription factors CCAAT/enhancer-binding protein-beta and -alpha and peroxisome proliferator-activated receptor-gamma and severely suppressed adipocyte differentiation as a result of defective adipogenic signaling. We conclude that galectin-12 is required for signal transduction that conveys hormone stimulation to the induction of adipogenic factors essential for adipocyte differentiation. The findings suggest that galectin-12 is a major regulator of adipose tissue development.

3T3 Cells↗

PubMed2001

Galectin-7 (PIG1) exhibits pro-apoptotic function through JNK activation and mitochondrial cytochrome c release.

Galectin-7 is normally expressed in all types of stratified epithelia, but is significantly down-regulated in squamous cell carcinomas. This protein was recently found to be highly inducible by p53 in a colon carcinoma cell line, DLD-1, and designated as PIG1 (for p53-induced gene 1). We studied transfectants of HeLa and DLD-1 cells ectopically expressing this protein and found that they were more susceptible to apoptosis than control transfectants. This was observed in apoptosis induced by mechanistically distinct stimuli, suggesting that galectin-7 acts on a common point in the apoptosis signaling pathways. Further analyses of actinomycin D-induced apoptosis demonstrated that galectin-7 expression causes enhanced caspase-3 activity and poly(ADP-ribose) polymerase cleavage, and the potentiation of apoptosis by galectin-7 was completely abrogated by a caspase inhibitor, benzyloxycarbonyl-Val-Ala-Asp-fluoromethyl ketone. In addition, galectin-7 transfectants displayed accelerated mitochondrial cytochrome c release and up-regulated JNK activity upon apoptosis induction. Several lines of evidence indicate that the effect on apoptosis is not due to the lectin functioning extracellularly through interactions with cell surface glycoconjugates. In fact, this lectin is found to localize in nuclei and cytoplasm of the transfectants and the transformed keratinocyte line HaCaT. Therefore, galectin-7 is a pro-apoptotic protein that functions intracellularly upstream of JNK activation and cytochrome c release. DNA microarray analysis revealed genes that are differentially expressed between galectin-7 and control transfectants. Some of them are potentially contributory to this lectin's proapoptotic function and these include redox-related genes monoamine oxidase B, ryanodine receptor 2, and glutathione S-transferase Mu 3.

Apoptosis↗

PubMedDate not supplied

Roles of galectin-3 in immune responses.

Galectins are a family of animal lectins with conserved carbohydrate-recognition domains for beta-galactoside. Galectin-3 is the only family member that is composed of a glycine/prolinerich N-terminal repeated sequence and a C-terminal carbohydrate-binding domain.Multiple functions of galectin-3 have been reported, depending on its location. Extracellular galectin-3 can bind to cell surface through glycosylated proteins and thereby trigger or modulate cellular responses such as mediator release or apoptosis. Intracellular galectin-3 has been reported to inhibit apoptosis, regulate the cell cycle, and participate in the nuclear splicing of pre-mRNA. Recent studies have revealed that galectin-3 is expressed in a variety of cell types in the immune system, constitutively or in response to microbial invasion. These studies implicate galectin-3 in both innate and adaptive immune responses, where it participates in the activation or differentiation of immune cells. This review summarizes the roles of galectin-3 in the immune system and discusses the possible underlying mechanisms.

Animals↗