Current Protein and Peptide Science - Volume 18, Issue 8, 2017

Parvalbumin (PA) is a classical small, mostly cytosolic Ca2+-binding protein of the EF-hand superfamily expressed in vertebrates in a tissue- and cell-specific manner, serving as a magnesium/ calcium buffer. In the last decade novel data were published on structural peculiarities of PA, likely affecting its functionality. This review sums up these findings and discusses their potential physiological significance.

There is growing recognition that composition and metabolic activity of the gut microbiota can be modulated by the dietary proteins which in turn impact health. The amino acid composition and digestibility of proteins, which are influenced by its source and amount of intake, play a pivotal role in determining the microbiota. Reciprocally, it appears that the gut microbiota is also able to affect protein metabolism which gives rise to the view that function between the microbiota and protein can proceed in both directions. In response to the alterations in dietary protein components, there are significant changes in the microbial metabolites including short chain fatty acids (SCFAs), ammonia, amines, gases such as hydrogen, sulfide and methane which are cytotoxins, genotoxins and carcinogens associated with development of colon cancer and inflammatory bowel diseases. A suitable ratio between protein and carbohydrate or even a low protein diet is recommended based on the evidence that excessive protein intake adversely affects health. Supplying high and undigested proteins will encourage pathogens and protein-fermenting bacteria to increase the risk of diseases. These changes of microbiota can affect the gut barrier and the immune system by regulating gene expression in relevant signaling pathways and by regulating the secretion of metabolites. The objective of this review is to assess the impact of dietary proteins on microbiota composition and activity in the gastrointestinal tract. Attention should be given to the dietary strategies with judicious selection of source and supplementation of dietary protein to benefit gut health.

In 2004, the first nonpeptide selective angiotensin II type 2 receptor (AT2R) agonist was reported. This nonpeptide (C21), which, exerts anti-inflammatory and antifibrotic actions in vivo, has been extensively explored and is currently in clinical trials. Subsequently, a large number of related drug-like AT2R agonists have been disclosed. Reviews that summarize known structure-activity relationships (SAR) of nonpeptide AT2R agonists have recently appeared in the literature; however, very few reviews discuss the role of angiotensin peptides as AT2R agonists. Furthermore, to date, there have been no reports focusing on the medicinal chemistry perspective of peptide AT2R agonists. In the present review, reports on linear and conformationally constrained Ang II analogues, with a focus on AT2R selective ligands that are proven to act as agonists at the AT2 receptor are summarized. The impact of truncations and macrocyclizations of Ang II analogues and of incorporation of scaffolds that mimic secondary structures into Ang II related peptides is highlighted. A survey of the efforts to transform the nonselective octapeptide Ang II to more drug-like selective AT2R agonists is presented. The relationship between the structures of the AT2R agonists and their affinity to the AT2R is briefly discussed and common pharmacophore elements of AT2R selective Ang II peptide analogues and selective nonpeptide AT2R agonists are compared.

Tribbles homolog 3 (TRIB3) is a mammalian gene that is upregulated in response to several types of cell death-inducing cellular stress. The TRIB3 protein is a pseudokinase, a protein kinase-like scaffold with impaired catalytic activity. However, research has revealed it to be prolific at forming protein– protein interactions. By binding to and regulating the activity of several key proteins, including the protein kinase Akt and transcription factors ATF4, CHOP and NF-ΚB, TRIB3 is at a junction of several signaling pathways. This review begins by providing insights into the characteristic protein structure and gene expression regulation mechanisms of TRIB3. Further, the diverse reported molecular roles of TRIB3 as a regulator of cell death, stress responses, inflammation, cell differentiation, protein degradation and other processes are discussed. Special attention is devoted to the involvement of TRIB3 in the pathogenesis of cancer and type 2 diabetes, two fields where TRIB3 has generated particular interest, as well as considerable debate, from a biomedical standpoint. Throughout, emphasis is placed on results obtained from animal models with altered TRIB3 expression (Trib3 knockout or overexpression mice), in order to provide insight into the contributions of TRIB3 to physiology and disease at the organism level.

Dipeptidyl peptidases (DPPs) belong to one of the protease families classified under EC 3.4.14 in the Nomenclature Committee of the International Union of Biochemistry and Molecular Biology. DPPs family consists of eight members in the mammalian species. They play a role in oligopeptide N-terminal processing and degradation of bioactive peptides. Over the past 20 years, most of the studies have been focused on DPP 4 that has important roles in metabolism and immunity. A large number of pharmacological inhibitors against DPP 4 have been tested rigorously and some of them are now used in the treatment of type 2 diabetes and obesity. In addition, current researches cast a spotlight on other physiological and pathological functions of DPP family members such as DPP 3 for the purpose of investigating their application as novel therapeutic compounds. In this review, we provide an update about the pathophysiological functions of DPPs, and discuss the future potential of the DPP family as pharmacological and therapeutic agents and targets.

Bioactive molecules such as peptides and proteins can optimize the repair of bone tissue; however, the results are often unpredictable when administered alone, owing to their short biological half-life and instability. Thus, the development of bioactive molecule-loaded drug delivery systems (DDS) to repair bone tissue has been the subject of intense research. DDS can optimize the repair of bone tissue owing to their physicochemical properties, which improve cellular interactions and enable the incorporation and prolonged release of bioactive molecules. These characteristics are fundamental to favor bone tissue homeostasis, since the biological activity of these factors depends on how accessible they are to the cell. Considering the importance of these DDS, this review aims to present relevant information on DDS when loaded with osteogenic growth peptide and bone morphogenetic protein. These are bioactive molecules that are capable of modulating the differentiation and proliferation of mesenchymal cells in bone tissue cells. Moreover, we will present different approaches using these peptide and protein-loaded DDS, such as synthetic membranes and scaffolds for bone regeneration, synthetic grafts, bone cements, liposomes, and micelles, which aim at improving the therapeutic effectiveness, and we will compare their advantages with commercial systems.

The aim of this review is to cover most recent research on plant pathogenesis- and defenserelated proteins from latex-bearing medicinal plant Chelidonium majus (Papaveraceae) in the context of its importance for latex activity, function, pharmacological activities, and antiviral medicinal use. These results are compared with other latex-bearing plant species and recent research on proteins and chemical compounds contained in their latex. This is the first review, which clearly summarizes pathogenesisrelated (PR) protein families in latex-bearing plants pointing into their possible functions. The possible antiviral function of the latex by naming the abundant proteins present therein is also emphasized. Finally latex-borne defense system is hypothesized to constitute a novel type of preformed immediate defense response against viral, but also non-viral pathogens, and herbivores.