Filaggrin inhibits generation of CD1a neolipid antigens by house dust mite-derived phospholipase.

Atopic dermatitis is a common pruritic skin disease in which barrier dysfunction and cutaneous inflammation play a role in pathogenesis. Mechanisms underlying the associated inflammation are not fully understood, and while CD1a-expressing Langerhans cells are known to be enriched within lesions, their role in clinical disease pathogenesis has not been studied. Here we observed that house dust mite (HDM) generates neolipid antigens for presentation by CD1a to T cells in the blood and skin lesions of affected individuals. HDM-responsive CD1a-reactive T cells increased in frequency after birth and showed rapid effector function, consistent with antigen-driven maturation. To define the underlying mechanisms, we analyzed HDM-challenged human skin and observed allergen-derived phospholipase (PLA2) activity in vivo. CD1a-reactive T cell activation was dependent on HDM-derived PLA2 and such cells infiltrated the skin after allergen challenge. Filaggrin insufficiency is associated with atopic dermatitis, and we observed that filaggrin inhibits PLA2 activity and inhibits CD1a-reactive PLA2-generated neolipid-specific T cell activity from skin and blood. The most widely used classification schemes of hypersensitivity, such as Gell and Coombs are predicated on the idea that non-peptide stimulants of T cells act as haptens that modify peptides or proteins. However our results point to a broader model that does not posit haptenation, but instead shows that HDM proteins generate neolipid antigens which directly activate T cells. Specifically, the data identify a pathway of atopic skin inflammation, in which house dust mite-derived phospholipase A2 generates antigenic neolipids for presentation to CD1a-reactive T cells, and define PLA2 inhibition as a function of filaggrin, supporting PLA2 inhibition as a therapeutic approach

Effect of copper upon the actions of sulphate-reducing bacteria isolated from soil contaminated by crude oil and heavy metals / Wpływ miedzi na aktywność bakterii redukujących siarczany wyizolowanych z gleby zanieczyszczonej ropą naftową i metalami ciężkimi

Przedmiot badań stanowiły sulfidogenne zespoły mikroorganizmów wyizolowane z gleby zanieczyszczonej ropą naftową i metalami ciężkich. Próbki gleby pochodziły z obszarów wybranych kopalni ropy naftowej w południowo-wschodniej Polsce. Celem badań było określenie wpływu stężenia metali ciężkich (miedzi) na aktywność wyselekcjonowanych zespołów mikroorganizmów

Dual catalytic role of the metal ion in nickel-assisted peptide bond hydrolysis

In our previous research we demonstrated the sequence specific peptide bond hydrolysis of the R1-(Ser/Thr)- Xaa-His-Zaa-R2 in the presence of Ni(II) ions. The molecular mechanism of this reaction includes an N–O acyl shift of the R1 group from the Ser/Thr amine to the side chain hydroxyl group of this amino acid. The proposed role of the Ni(II) ion is to establish favorable geometry of the reacting groups. In this work we aimed to find out whether the crucial step of this reaction – the formation of the intermediate ester – is reversible. For this purpose we synthesized the test peptide Ac-QAASSHEQA-am, isolated and purified its intermediate ester under acidic conditions, and reacted it, alone, or in the presence of Ni(II) or Cu(II) ions at pH 8.2. We found that in the absence of either metal ion the ester was quickly and quantitatively (irreversibly) rearranged to the original peptide. Such reaction was prevented by either metal ion. Using Cu(II) ions as CD spectroscopic probe we showed that themetal binding structures of the ester and the final amine are practically identical. Molecular calculations of Ni(II) complexes indicated the presence of steric strain in the substrate, distorting the complex structure from planarity, and the absence of steric strain in the reaction products. These results demonstrated the dual catalytic role of the Ni(II) ion in this mechanism. Ni(II) facilitates the acyl shift by setting the peptide geometry, and prevents the reversal of the acyl shift, by stabilizing subsequent reaction products

Ni2+-Assisted Hydrolysis May Affect the Human Proteome; Filaggrin Degradation Ex Vivo as an Example of Possible Consequences

Deficiency in a principal epidermal barrier protein, filaggrin (FLG), is associated with multiple allergic manifestations, including atopic dermatitis and contact allergy to nickel. Toxicity caused by dermal and respiratory exposures of the general population to nickel-containing objects and particles is a deleterious side effect of modern technologies. Its molecular mechanism may include the peptide bond hydrolysis in X1-S/T-c/p-H-c-X2 motifs by released Ni2+ ions. The goal of the study was to analyse the distribution of such cleavable motifs in the human proteome and examine FLG vulnerability of nickel hydrolysis. We performed a general bioinformatic study followed by biochemical and biological analysis of a single case, the FLG protein. FLG model peptides, the recombinant monomer domain human keratinocytes in vitro and human epidermis ex vivo were used. We also investigated if the products of filaggrin Ni2+-hydrolysis affect the activation profile of Langerhans cells. We found X1-S/T-c/p-H-c-X2 motifs in 40% of human proteins, with the highest abundance in those involved in the epidermal barrier function, including FLG. We confirmed the hydrolytic vulnerability and pH-dependent Ni2+-assisted cleavage of FLG-derived peptides and FLG monomer, using in vitro cell culture and ex-vivo epidermal sheets; the hydrolysis contributed to the pronounced reduction in FLG in all of the models studied. We also postulated that Ni-hydrolysis might dysregulate important immune responses. Ni2+-assisted cleavage of barrier proteins, including FLG, may contribute to clinical disease associated with nickel exposure

Corrigendum: Ni 2+ -assisted hydrolysis may affect the human proteome; filaggrin degradation ex vivo as an example of possible consequences

Peer reviewed: Tru

Ni2+-Assisted Hydrolysis May Affect the Human Proteome; Filaggrin Degradation Ex Vivo as an Example of Possible Consequences.

Peer reviewed: TrueAcknowledgements: We thank MSc Małgorzata Orłowska for her help with the iTOL visualization.Deficiency in a principal epidermal barrier protein, filaggrin (FLG), is associated with multiple allergic manifestations, including atopic dermatitis and contact allergy to nickel. Toxicity caused by dermal and respiratory exposures of the general population to nickel-containing objects and particles is a deleterious side effect of modern technologies. Its molecular mechanism may include the peptide bond hydrolysis in X1-S/T-c/p-H-c-X2 motifs by released Ni2+ ions. The goal of the study was to analyse the distribution of such cleavable motifs in the human proteome and examine FLG vulnerability of nickel hydrolysis. We performed a general bioinformatic study followed by biochemical and biological analysis of a single case, the FLG protein. FLG model peptides, the recombinant monomer domain human keratinocytes in vitro and human epidermis ex vivo were used. We also investigated if the products of filaggrin Ni2+-hydrolysis affect the activation profile of Langerhans cells. We found X1-S/T-c/p-H-c-X2 motifs in 40% of human proteins, with the highest abundance in those involved in the epidermal barrier function, including FLG. We confirmed the hydrolytic vulnerability and pH-dependent Ni2+-assisted cleavage of FLG-derived peptides and FLG monomer, using in vitro cell culture and ex-vivo epidermal sheets; the hydrolysis contributed to the pronounced reduction in FLG in all of the models studied. We also postulated that Ni-hydrolysis might dysregulate important immune responses. Ni2+-assisted cleavage of barrier proteins, including FLG, may contribute to clinical disease associated with nickel exposure