Metabolomic and lipidomic fingerprints in inflammatory skin diseases - Systemic illumination of atopic dermatitis, hidradenitis suppurativa and plaque psoriasis.

Auto-inflammatory skin diseases place considerable symptomatic and emotional burden on the affected and put pressure on healthcare expenditures. Although most apparent symptoms manifest on the skin, the systemic inflammation merits a deeper analysis beyond the surface. We set out to identify systemic commonalities, as well as differences in the metabolome and lipidome when comparing between diseases and healthy controls. Lipidomic and metabolomic LC-MS profiling was applied, using plasma samples collected from patients suffering from atopic dermatitis, plaque-type psoriasis or hidradenitis suppurativa or healthy controls. Plasma profiles revealed a notable shift in the non-enzymatic anti-oxidant defense in all three inflammatory disorders, placing cysteine metabolism at the center of potential dysregulation. Lipid network enrichment additionally indicated the disease-specific provision of lipid mediators associated with key roles in inflammation signaling. These findings will help to disentangle the systemic components of autoimmune dermatological diseases, paving the way to individualized therapy and improved prognosis.

The interaction of myristylated peptides with the catalytic domain of protein kinase C revealed by their sequence palindromy and the identification of a myristyl binding site.

Using a model of the enzyme structure and the results from a series of free and myristylated peptides, we provide evidence that peptides corresponding to the pseudosubstrate sequence of protein kinase C bind to the enzyme substrate binding site in an essentially extended conformation. This and the nearly symmetrical location of positive charges around the substrate phosphoritable site allow the peptide to bind to the enzyme in either an N-to-C orientation or its C-to-N opposite orientation. The latter is favoured by a change in residue chirality or when the peptide bears a myristoyl chain at its N-terminus. A myristyl binding site was also identified in the enzyme structure and its location in a region proximal to the C-terminal residue of pseudosubstrate bound in the N-to-C direction suggested that C-myristylation of peptide substrates should be more effective than N-myristoylation in antagonizing the enzyme. A peptide (H-RFARKGALRQKN-CONH-Myr) which contains the myristyl chain covalently linked to the C-terminal residue of the pseudosubstrate was thus made and shown to be a potent inhibitor of the histone kinase reaction of protein kinase C and the phosphorylation of p47 in intact cells.

Rational design of a new C-myristylamido peptide exerting potent and selective PKC inhibitory activity.

A 3D model of the catalytic domain of PKC was built based on the X-ray structure of the homologous PKA enzyme. The two enzymes were found to have similar general architecture although differing for the number of negatively charged clusters and their location near the phosphorylation site. These differences were consistent with the charge requirements deduced from the consensus sequence of PKC and PKA substrates. A Myristyl Binding Site (MBS) was found in the PKC model between helix C and sheets 8 and 9. The identification of this MBS allowed the rationalization of the results obtained with N-myristoylated peptide inhibitors and, above all, the design of ITF1671 (H-RFARKGALRQKN-CONH-Myr), a new C-myristylamido peptide, which exerted one of the most potent inhibitory activity against PKC and PKM known to-date.