Dermcidin

Mammals protect themselves from inflammation triggered by microorganisms through secretion of antimicrobial peptides (AMPs). One mechanism by which AMPs kill bacterial cells is perforating their membranes. Membrane interactions and pore formation were investigated for α-helical AMPs leading to the formulation of three basic mechanistic models: the barrel stave, toroidal, and carpet model. One major drawback of these models is their simplicity. They do not reflect the realin vitroandin vivoconditions. To challenge and refine these models using a structure-based approach we set out to investigate how human cathelicidin (LL-37) and dermcidin (DCD) interact with membranes. Both peptides are α-helical and their structures have been solved at atomic resolution. DCD assembles in solution into a hexameric pre-channel complex before the actual membrane targeting and integration step can occur, and the complex follows a deviation of the barrel stave model. LL-37 interacts with lipids and shows the formation of oligomers generating fibril-like supramolecular structures on membranes. LL-37 further assembles into transmembrane pores with yet unknown structure expressing a deviation of the toroidal pore model. Both of their specific targeting mechanisms will be discussed in the context of the "old" models propagated in the literature.

Antimicrobial peptides (AMPs) are important effector molecules of the innate immune defense of diverse species. The majority of known AMPs are cationic therefore facilitating the initial binding of the positively charged peptides to the negatively charged bacterial membrane. Dermcidin (DCD) is constitutively expressed in eccrine sweat glands, secreted into sweat and transported to the epidermal surface where it is proteolytically processed giving rise to several truncated DCD peptides. Its processed forms such as the anionic 48mer DCD-1L and the 47mer DCD-1 possess antimicrobial activity against numerous bacteria including Staphylococcus aureus. Here, the latest knowledge regarding the mode of action of the anionic DCD-1(L) and the functional consequences of their interaction with bacterial membranes is reviewed. There is evidence that the interaction of DCD-1(L) with negatively charged bacterial phospholipids leads to Zn(2+) dependent formation of oligomeric complexes in the bacterial membrane, which subsequently leads to ion channel formation resulting in membrane depolarization and bacterial cell death.

Purpose of review:The diverse protein products of the dermcidin gene are relevant to immunity, cancer cell progression and cancer cachexia. This article evaluates recent developments/controversies around dermcidin.Recent findings:Dermcidin has recently been shown to act as a survival/proliferation factor in hepatoma and prostate cancer cell lines. Recent studies suggest that the Y-P30 subunit of the dermcidin polypeptide offers a survival advantage in such cancer cells. Nevertheless, the relevance of Y-P30 to cancer growth in vivo, and mechanisms of action remain unknown. In mice, tumour cells appear to glycosylate the Y-P30 subunit, transforming it into a potent skeletal muscle proteolysis-inducing factor. Recent work has described a receptor and signal transduction pathways for murine glycosylated proteolysis-inducing factor. The absence of classical N-glycosylation sites in the human proteolysis-inducing factor peptide and the lack of specific tools for the detection of the key carbohydrate moieties conferring the proteolysis-inducing activity, however, remain barriers to confirming glycosylated proteolysis-inducing factor as a pro-cachectic factor in humans.Summary:There is a growing body of evidence illustrating dermcidin as an oncogene and Y-P30 as a survival factor. The biology of murine proteolysis-inducing factor as a pro-cachectic factor continues to evolve; however, its role in human biology remains speculative.