Multiple clinical forms of dehydrated hereditary stomatocytosis arise from mutations in PIEZO1

Autosomal dominant dehydrated hereditary stomatocytosis (DHSt) usually presents as a compensated hemolytic anemia with macrocytosis and abnormally shaped red blood cells (RBCs). DHSt is part of a pleiotropic syndrome that may also exhibit pseudohyperkalemia and perinatal edema. We identified PIEZO1 as the disease gene for pleiotropic DHSt in a large kindred by exome sequencing analysis within the previously mapped 16q23-q24 interval. In 26 affected individuals among 7 multigenerational DHSt families with the pleiotropic syndrome, 11 heterozygous PIEZO1 missense mutations cosegregated with disease. PIEZO1 is expressed in the plasma membranes of RBCs and its messenger RNA, and protein levels increase during in vitro erythroid differentiation of CD341 cells. PIEZO1 is also expressed in liver and bone marrow during human and mouse development. We suggest for the first time a correlation between a PIEZO1 mutation and perinatal edema. DHSt patient red cells with the R2456H mutation exhibit increased ion-channel activity. Functional studies of PIEZO1 mutant R2488Q expressed in Xenopus oocytes demonstrated changes in ion-channel activity consistent with the altered cation content of DHSt patient red cells. Our findings provide direct evidence that R2456H and R2488Q mutations in PIEZO1 alter mechanosensitive channel regulation, leading to increased cation transport in erythroid cells

Structure-function relationships and conformational properties of alpha-MSH(6-13) analogues with candidacidal activity

alpha-Melanocyte-stimulating hormone (alpha-MSH) is an endogenous linear tridecapeptide with potent anti-inflammatory effects. We firstly demonstrated that alpha-MSH and its C-terminal sequence Lys-Pro-Val [alpha-MSH(11-13)] have antimicrobial effects against two major and representative pathogens: Staphylococcus aureus and Candida albicans. Successively, in an attempt to improve the candidacidal activity of alpha-MSH and to better understand the peptide structure-antifungal activity relations, we have recently designed and synthesized novel peptide analogues. We focused on the sequence alpha-MSH(6-13), which contains the invariant melanocortin core sequence His-Phe-Arg-Trp (6-9) and also contains the sequence Lys-Pro-Val (11-13) important for antimicrobial activity. In that structure-activity study, we discovered several compounds that have greater candidacidal activity than alpha-MSH, among which the peptide [D-Nal-7,Phe-12]-alpha-MSH(6-13) was the most potent. Here, we report a detailed conformational analysis by spectroscopic and computational methods of three peptides, alpha-MSH(6-13) (1), [D-Nal-7,Phe-12]-alpha-MSH(6-13) (2) and [D-Nal-7,Asp-12]-alpha-MSH(6-13) (3). Peptides were chosen on the basis of their candidacidal activities and were studied in membrane mimetic environment (SDS micelles). Different turn structures were observed for the three peptides and a conformation-activity model was developed based on these results. This study offers a structural basis for the design of novel peptide and non-peptide analogues to be used as new antimicrobial agent

Alanine scanning analysis and structure–function relationships of the frog-skin antimicrobial peptide temporin-1Ta

The increasing resistance of bacteria and fungi to the available antibiotic/antimycotic drugs urges for a search for new anti-infective compounds with new modes of action. In line of this, natural CAMPs represent promising and attractive candidates. Special attention has been devoted to frog-skin temporins, because of their short size (10-14 residues long) and their unique features. In particular, temporin-1Ta has the following properties: (i) it is mainly active on Gram-positive bacteria; (ii) it can synergize, when combined with temporin-1Tl, in inhibiting both gram-negative bacterial growth and the toxic effect of LPS; (iii) it preserves biological activity in the presence of serum; and (iv) it is practically not hemolytic. Rational design of CAMPs represents a straightforward approach to obtain a peptide with a better therapeutic index. Here, we used alanine scanning analogs to elucidate the contribution of the side chains of each amino acid residue to the peptide's antimicrobial and hemolytic activity. Beside providing insight into the biophysical attributes and the critical positions within the peptide sequence, which govern the antimicrobial/hemolytic activity of this temporin isoform, our studies assist in optimizing the design of temporin-based lead structures for the production of new anti-infective agents