Design and synthesis of peptides as stabilizers of histone deacetylase 4

Histone deacetylase 4 (HDAC4) contributes to gene repression by complex formation with HDAC3 and the corepressor silencing mediator for retinoid or thyroid hormone receptors (SMRT). We hypothesized that peptides derived from the class IIa specific binding site of SMRT would stabilize a specific conformation of its target protein and modulate its activity. Based on the SMRT-motif 1 (SM1) involved in the interaction of SMRT with HDAC4, we systematically developed cyclic peptides that exhibit Ki values that are 9 to 56 times lower than that of the linear SMRT peptide. The peptide macrocycles stabilize the wildtype of the catalytic domain of HDAC4 (cHDAC4) considerably better than its thermally more stable 'gain-of-function' (GOF) variant, cHDAC4-H976Y. Molecular docking and mutagenesis studies indicated that the cyclic peptides bind in a similar but not identical manner as the linear SMRT peptide to a discontinuous binding site. Ion mobility mass spectrometry showed no major changes in the protein fold upon peptide binding. Consistent with these results, preliminary hydrogen-deuterium exchange mass spectrometry measurements indicated only minor conformational changes. Taken together, the cyclic SMRT peptides most likely stabilize the apo form of cHDAC4.

Screening of Peptides that Specifically Binds to M3-M4 Extracellular Domain of Sodium Pump α1 Subunit and Analysis of Their Bioactivity In Vitro and In Vivo

Interaction between ouabain (OUA) and Na+/K+-pump remains in the current focus of hypertension research. This study aimed to find an oligopeptide that would antagonize the inhibitory effect of endogenous OUA on Na+/K+-pump and examine its activity at the cellular and organism levels. To this end, Phage Random 12 Peptide Library was employed to screen for specific polypeptide ligands that interact with M3-M4 extracellular domain of Na+/K+-pump α1 subunit known as OUA-binding site. Synthetic sequence ILEYTWLEAGGGS of extracellular domain M3-M4 of Na+/K+-pump α1 subunit was used as the target. The phage positive clones were screened and identified using the phage library and double sandwich ELISA. DNA was extracted and sequenced to synthesize 3 peptide ligands to Na+/K+-pump: P-A, P-B, and P-C. We also studied the effects of the short peptide with the highest potency for countering OUA on proliferation and apoptosis of EA.hy926 vascular endothelial cells and on systolic BP in spontaneously hypertensive rats (SHR). The effect of peptide P-A on proliferation (stimulation with physiological concentrations of OUA) and on apoptosis (stimulation with OUA in high concentrations) of EA.hy926 vascular endothelial cells was assessed by the MTT test and flow cytometry, respectively. In SHR rats, intravenous injection of P-A decreased systolic BP. Oligopeptide P-A competitively antagonized the inhibitory action of OUA on Na+/K+-pump, OUA-induced proliferation, and OUA-provoked apoptosis of cultured EA.hy926 cells. Our findings open vista for the emergence of novel hypertensive drugs.

3D-Printed Porous Scaffolds of Hydrogels Modified with TGF-β1 Binding Peptides to Promote In Vivo Cartilage Regeneration and Animal Gait Restoration

The treatment of cartilage injury and osteoarthritis has been a classic problem for many years. The idea of in situ tissue regeneration paves a way for osteochondral repair in vivo. Herein, a hydrogel scaffold linked with bioactive peptides that can selectively adsorb transforming growth factor β1 (TGF-β1) was hypothesized to not only afford cell ingrowth space but also induce the endogenous TGF-β1 recruitment for chondrogenesis promotion. In this study, bilayered porous scaffolds with gelatin methacryloyl (GelMA) hydrogels as a matrix were constructed via three-dimensional (3D) printing, of which the upper layer was covalently bound with bioactive peptides that can adsorb TGF-β1 for cartilage repair and the lower layer was blended with hydroxyapatite for subchondral regeneration. The scaffolds showed promising therapeutic efficacy proved by cartilage and osteogenic induction in vitro and osteochondral repair of rats in vivo. In particular, the animal gait behavior was recovered after the in situ tissue regeneration, and the corresponding gait analysis demonstrated the promotion of tissue regeneration induced by the porous hydrogels with the binding peptides.

Man-Made Synthetic Receptors for Capture and Analysis of Ochratoxin A

Contemporary analytical methods have the sensitivity required for Ochratoxin A detection and quantification, but direct application of these methods on real samples can be rarely performed because of matrix complexity. Thus, efficient sample pre-treatment methods are needed. Recent years have seen the increasing use of artificial recognition systems as a viable alternative to natural receptors, because these materials seem to be particularly suitable for applications where selectivity for Ochratoxin A is essential. In this review, molecularly imprinted polymers, aptamers and tailor-made peptides for Ochratoxin A capture and analysis with particular attention to solid phase extraction applications will be discussed.