Identification of plasma membrane glycoproteins involved in the contact-dependent inhibition of growth of diploid human fibroblasts

Circulating miRNAs and tissue iron overload in transfusion-dependent β-thalassemia major: novel predictors and follow-up guide

Tissue iron overload is a life-threatening scenario in children with transfusion-dependent β-thalassemia major, miRNAs that are involved in iron hemostasis could serve as therapeutic targets for control of iron overload. We aimed to find out the association between three iron-related miRNAs "miR-let-7d, miR-122, and miR-200b" and excess iron in tissues, in transfusion-dependent β-thalassemia major patients. Circulating miRNA expressions are measured in peripheral blood (PB) samples using qPCR of transfusion-dependent (TDT) β-thalassemia patients (n = 140) and normalized to non-transfusion-dependent (NTDT) β-thalassemia (n = 45). Results revealed that plasma expression levels of miR-let-7d and miR-200b were significantly downregulated in TDT patients; however, miR-122 was upregulated. In terms of tissue iron load, aberrant expression of miRNAs was significantly associated with increased-iron accumulation in hepatic and cardiac tissues. We concluded that circulating miRNAs are strong candidates that associate iron hemostasis in transfusion-dependent β-thalassemia major patients. And by extension, targeting miR-let-7d, miR-122, and miR-200 might serve as novel sensitive, specific and non-invasive predictor biomarkers for cellular damage under condition of tissue iron excess.

Purification and stability characterization of a cell regulatory sialoglycopeptide inhibitor

Previous attempts to physically separate the cell cycle inhibitory and protease activities in preparations of a purified cell regulatory sialoglycopeptide (CeReS) inhibitor were largely unsuccessful. Gradient elution of the inhibitor preparation from a DEAE HPLC column separated the cell growth inhibitor from the protease, and the two activities have been shown to be distinct and non-overlapping. The additional purification increased the specific biological activity of the CeReS preparation by approximately two-fold. The major inhibitory fraction that eluted from the DEAE column was further analyzed by tricine-SDS-PAGE and microbore reverse phase HPLC and shown to be homogeneous in nature. Two other fractions separated by DEAE HPLC, also devoid of protease activity, were shown to be inhibitory to cell proliferation and most likely represented modified relatives of the CeReS inhibitor. The highly purified CeReS was chemically characterized for amino acid and carbohydrate composition and the role of the carbohydrate in cell proliferation inhibition, stability, and protease resistance was assessed.

Perturbing cell surface beta-(1,4)-galactosyltransferase on F9 embryonal carcinoma cells arrests cell growth and induces laminin synthesis

Cell growth and differentiation are influenced by intercellular contact, suggesting that cell adhesion molecules may be instrumental in triggering these events. F9 embryonal carcinoma cells are an ideal system in which to examine the function of cell adhesion molecules in growth and differentiation, since the relevant cell adhesion molecules and differentiation markers are well defined. Intercellular adhesion in F9 cells is mediated by uvomorulin, or E-cadherin, and cell surface beta-(1,4)-galactosyltransferase. Since previous studies suggested that neither F9 cell growth nor differentiation is directly dependent on uvomorulin function, in this study we examined whether cell surface galactosyltransferase plays any role in F9 cell growth or differentiation. A variety of galactosyltransferase perturbants, including anti-galactosyltransferase antibodies, UDPgalactose, and the substrate modifier protein alpha-lactalbumin, inhibited the growth of F9 cells, whereas control reagents did not. To examine this in more detail, we analyzed the effects of perturbing surface galactosyltransferase on progression through the F9 cell cycle. Anti-galactosyltransferase IgG treatment inhibited ornithine decarboxylase activity and lengthened the F9 cell cycle during G1 and G2, the latter mimicking the effects of retinoic acid, a reagent known to prolong the F9 cell cycle and induce differentiation. In contrast, anti-uvomorulin antibodies had no effect on F9 cell growth, ornithine decarboxylase activity, or progression through the cell cycle. Furthermore, perturbation of surface galactosyltransferase adhesions in F9 cell aggregates induced precocious F9 cell differentiation, as assayed by increased laminin synthesis, whereas control reagents had no effect. Thus, perturbing surface galactosyltransferase adhesions in F9 cells both decreases growth and stimulates synthesis of laminin. These results imply that interactions between surface galactosyltransferase and its oligosaccharide ligand during cell adhesion may affect the normal growth-regulatory and differentiation-inducing signals, as is seen, in part, during treatment with retinoic acid.

Evidence that filopodia outgrowth is a common final pathway for fibroblast growth inhibition in vitro

To identify events associated with fibroblast growth inhibition, the effect of two known inhibitors, interferon-alpha and all-trans retinoic acid, on the growth and surface morphology of cultured fibroblasts was examined. Interferon-alpha administered at seeding reduced both growth rate and saturation density; all-trans retinoic acid reduced only saturation density. However, both negative growth modulators were associated with an increase in filopodia outgrowth and an increase in intracellular filamentous actin in a time course corresponding to onset of growth inhibition by these agents. In combination with earlier findings, these data suggested that, regardless of etiology, cultured fibroblast growth restriction is mediated in part by an actin-dependent outgrowth of filopodia that augment intercellular contact.