Thymosin beta 4-like peptides

Studies on Orally Available Inhibitors of HIV Protease. Peptidyl Aldehydes and Trifluoromethyl Ketones

Low-molecular-weight peptidyl aldehyde inhibitors of HIV protease that reach in vivo plasma concentrations after oral administration substantiailly in excess of the antiviral IC90 are described. We also report efforts to improve the potency and stability of these compounds that culminated in a series of peptidyl trifluoromethyl ketones with increased potency but decreased bioavailability.

Beta thymosins as actin binding peptides

The beta thymosins are a highly conserved family of strongly polar 5 kDa polypeptides that are widely distributed among vertebrate classes; most are now known to bind to monomeric actin and inhibit its polymerization. One beta thymosin, beta four, (T beta 4) is the predominant form in mammalian cells, present at up to 0.5 mM. Many species are known to produce at least two beta thymosin isoforms, in some cases in the same cell. Their expression can be separately regulated. When present outside the cell, the N-terminal tetrapeptide of beta four appears to affect cell cycle regulation; beta thymosins or smaller fragments derived from them may have additional regulatory functions. We suggest that many developmental changes in beta thymosin levels within cells and tissues may be related to changes in G-actin pool size.

Low periconceptional maternal serum thymosin alpha 1 levels are associated with blighted pregnancies

OBJECTIVE

The thymus-derived peptides, thymosin alpha 1 and thymosin beta 4, are believed to contribute to the maintenance of immune homeostasis. They are also associated with the hypothalamic-pituitary-adrenal-gonadal axis and may play a role in reproduction.

STUDY DESIGN

Patients were recruited from a university hospital setting. Eligible candidates were 24 to 38 years old who were being seen in an ovulation induction and in vitro fertilization program. Serial maternal serum thymosin alpha 1 and beta 4 levels were assayed preconceptual and then twice in the first trimester by ELISA in 28 women with known ovulation dates who successfully conceived as demonstrated by positive serum beta human chorionic gonadotropin (hCG). Thymosin alpha 1 and beta 4 serum levels for viable pregnancies (group I; N = 19) were compared to pregnancies that aborted (group II; N = 9) using repeated measures of multivariate analysis of variance (MANOVA). Periconceptional (preovulatory and early pregnancy) thymosin alpha 1 and beta 4 values between groups I and II were compared using repeated measure one-way ANOVA.

RESULTS

Thymosin alpha 1 levels from pregnancies that remained viable were significantly higher than those from pregnancies that spontaneously aborted. Preovulation thymosin alpha 1 levels also tended to be lower in pregnancies that subsequently aborted. Thymosin beta 4 levels were similar between the two groups.

CONCLUSION

Decreased maternal serum thymosin alpha 1 levels may be associated with periconceptional endocrine and/or immune disturbances preceding miscarriage.

Small actin-binding proteins: the beta-thymosin family

Thymosin beta 4 is a major actin monomer binding protein present at high concentration in many vertebrate cells and cell lines. The interactions of actin with thymosin beta 4, actobindin and profilin are compared. Nine beta-thymosins have been identified; six have been shown to bind to actin. Regulation of the synthesis of thymosin beta 10 and thymosin beta 4 has been found in brain development and after stimulation of several cell types, respectively. The extracellular effects of thymosin beta 4 still need clarification.

Determination of thymosin beta 4 in human blood cells and serum

A simple one-step procedure for the determination of thymosin beta 4 in whole blood, various blood corpuscles, plasma and serum by reversed-phase high-performance liquid chromatography (HPLC) is described. The blood cells were isolated by a Ficoll density gradient technique. The isolated cells were lysed and deproteinized with perchloric acid in the presence of an internal standard. The supernatant solution was neutralized by potassium hydroxide solution and thymosin beta 4 was measured by HPLC without further manipulations. The following amounts (fg per cell) were determined: polymorphonuclear leukocytes (409), mononuclear leukocytes (267) and platelets (22.3). Erythrocytes contained no thymosin beta 4. The average concentration of thymosin beta 4 in an extract of whole blood was 16.3 micrograms/ml. The concentration in plasma was less than 1% of that value. However, if serum was prepared and not immediately removed from the clotted blood, the concentration of the peptide increased from 0.04 to 2.1 micrograms/ml within 24 h. The biological significance of the findings is discussed.