Staphylococcus pseudintermedius is a common commensal bacterium colonizing the skin and mucosal surfaces of household animals. However, it has recently emerged as a dangerous opportunistic pathogen, comparable to S. aureus for humans. The epidemiological situation is further complicated by the increasing number of methicillin-resistant S. pseudintermedius infections and evidence of gene transmission driving antibiotic resistance between staphylococci colonizing human and zoonotic hosts. In the present study, we describe a unique peptide, BacSp222, that possesses features characteristic of both bacteriocins and virulence factors. BacSp222 is secreted in high quantities by S. pseudintermedius strain 222 isolated from dog skin lesions. This linear, fifty-amino-acid highly cationic peptide is plasmid-encoded and does not exhibit significant sequence similarities to any other known peptides or proteins. BacSp222 kills gram-positive bacteria (at doses ranging from 0.1 to several micromol/l) but also demonstrates significant cytotoxic activities towards eukaryotic cells at slightly higher concentrations. Moreover, at nanomolar concentrations, the peptide also possesses modulatory properties, efficiently enhancing interferon gamma-induced nitric oxide release in murine macrophage-like cell lines. BacSp222 appears to be one of the first examples of multifunctional peptides that breaks the convention of splitting bacteriocins and virulence factors into two unrelated groups.

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Bradykinin-related peptides, universal mediators of infl ammation collectively referred to as the kinins, are often produced in excessive amounts during microbial infections. We have recently shown that the yeast Candida albicans , the major fungal pathogen to humans, can exploit two mechanisms to enhance kinin levels at the sites of candidial infection, one depending on adsorption and activation of the endogenous kinin-generating system of the host on the fungal cell wall and the other relying on cleavage of kinin precursors, the kininogens, by pathogen-secreted proteases. This work aimed at assigning this kininogenase activity to the major secreted aspartic protease of C. albicans (SAP2). The purifi ed SAP2 was shown to cleave human kininogens, preferably the low molecular mass form (LK) and optimally in an acidic environment (pH 3.5 -4.0), and to produce two kinins, Met-Lys-bradykinin and its derivative, [Hydroxyproline 3 ]-Met-Lys-bradykinin, both of which are capable of interacting with cellular bradykinin receptors of the B2 subtype. Additionally, albeit with a lower yield, des-Arg 9 -Met-Lysbradykinin, an effective agonist of B1-subtype receptors, was released. The pathophysiological potential of these kinins and des-Arg-kinin was also proven by presenting their ability to stimulate human promonocytic cells U937 to release proinfl ammatory interleukin 1 β (IL-1 β ) and IL-6.

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Yeast-like fungi from the Candida genus are predominantly harmless commensals that colonize human skin and mucosal surfaces, but under conditions of impaired host immune system change into dangerous pathogens. The pathogenicity of these fungi is typically accompanied by increased adhesion and formation of complex biofilms, making candidal infections challenging to treat. Although a variety of antifungal drugs have been developed that preferably attack the fungal cell wall and plasma membrane, these pathogens have acquired novel defense mechanisms that make them resistant to standard treatment. This causes an increase in the incidence of candidiasis and enforces the urgent need for an intensified search for new specifics that could be helpful, alone or synergistically with traditional drugs, for controlling Candida pathogenicity. Currently, numerous reports have indicated the effectiveness of plant metabolites as potent antifungal agents. These substances have been shown to inhibit growth and to alter the virulence of different Candida species in both the planktonic and hyphal form and during the biofilm formation. This review focuses on the most recent findings that provide evidence of decreasing candidal pathogenicity by different substances of plant origin, with a special emphasis on the mechanisms of their action. This is a particularly important issue in the light of the currently increasing frequency of emerging Candida strains and species resistant to standard antifungal treatment.

In recent years a wide range of studies have shown that G protein-coupled receptors modulate a variety of cell functions through the formation of dimers. For instance, there is growing evidence for the dimerization of bradykinin or dopamine receptors, both as homodimers and heterodimers. A discovery of direct interactions of angiotensin II receptors with bradykinin 2 receptor (B2R) or dopamine D2 (D2R) receptor has led to a hypothesis on a potential dimerization between two latter receptors. In this study, we have demonstrated a constitutive colocalization of receptors on the membranes of HEK293 cells transiently transfected with plasmid vectors encoding B2R and D2R, fused with fluorescent proteins. The receptor colocalization was significantly enhanced by specific agonists of B2R or D2R after 5min following the addition, whereas simultaneous stimulation with these agonists did not influence the B2R/D2R colocalization level. In addition, B2R-D2R heterodimerization was confirmed with FLIM-FRET technique. The most characteristic signaling pathways for B2R and D2R, dependent on intracellular Ca and cAMP concentration, respectively, were analyzed in cells presenting similar endogenous expression of B2R and D2R. Significant changes in receptors' signaling were observed after simultaneous stimulation with agonists, suggesting transformations in proteins' conformation after dimerization. The evidence of B2R-D2R dimerization may open new perspectives in the modulation of diverse cellular functions which depend on their activation.

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