Accumulating evidence indicates that IL-1 family members and Th17 cytokines have a pathogenic role in psoriasis. We investigated the regulatory interactions of the IL-1-like IL-36 cytokine family and the Th17 cytokines in the context of skin inflammation. We observed increased gene expression of all three IL-36 cytokines in a Th17-dominant psoriasis-like animal model. The induction was downregulated by neutralizing IL-22. Expression of the IL-36s was also induced in cultured primary human keratinocytes (KC) by IL-17A and tumor necrosis factor (TNF)-α, and IL-22 synergized with IL-17A and TNF-α. Furthermore, the IL-36s directly induced their own expression and the production of proinflammatory mediators (TNF-α, IL-6, IL-8) in KC. These functions were markedly enhanced with the addition of IL-17A or TNF-α to the cultures. Similarly, IL-36α and IL-36β augmented IL-17A-mediated induction of antibacterial peptides. Finally, we show that the increased gene expression of IL-36 correlated with Th17 cytokines in the lesions of psoriatic patients. Our results indicate that the IL-36 cytokines are not only regulated by Th17 cytokines, but that they themselves can regulate the expression and enhance the function of Th17 cytokines. We propose that a feedback loop between the IL-36 and Th17 cytokines is involved in driving cytokine expression in psoriatic tissues.

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Focal adhesions are sites of cell‐extracellular matrix interactions that function in anchoring stress fibers to the plasma membrane and in adhesion‐mediated signal transduction. Both focal adhesion structure and signaling ability involve protein tyrosine phosphorylation. LAR is a broadly expressed transmembrane protein tyrosine phosphatase comprised of a cell adhesion‐like ectodomain and two intracellular protein tyrosine phosphatase domains. We have identified a novel cytoplasmic 160 kDa phosphoserine protein termed LAR‐interacting protein 1 (LIP.1), which binds to the LAR membrane‐distal D2 protein tyrosine phosphatase domain and appears to localize LAR to focal adhesions. Both LAR and LIP.1 decorate the ends of focal adhesions most proximal to the cell nucleus and are excluded from the distal ends of focal adhesions, thus localizing to regions of focal adhesions presumably undergoing disassembly. We propose that LAR and LIP.1 may regulate the disassembly of focal adhesions and thus help orchestrate cell‐matrix interactions.

Dbl-homology guanine nucleotide exchange factors (DH-GEFs) regulate actin cytoskeletal reorganization, cell adhesion, and gene transcription via activation of Rho GTPases. However, little is known about the physiological role of mammalian DH-GEFs during development. The DH-GEF family member Trio is of particular interest because it is a multifunctional protein possessing two GEF domains, as well as a protein serine͞threonine kinase domain, and trio-like genes in Caenorhabditis elegans and Drosophila were shown to function in neural migration and axon guidance. To determine the role of Trio during mammalian development, we generated a mouse trio loss-of-function mutation (trio ؊/؊ ). Trio function is essential during late embryonic development as genotype analysis indicated that trio ؊/؊ embryos died between embryonic day (E)-15.5 and birth, or shortly thereafter. In the trio ؊/؊ embryos, primary skeletal myofibers were relatively normal at E14.5, but by E18.5 highly unusual spherical myofibers accumulated. Trio deficiency may cause a defect in secondary myogenesis, as the appearance of the abnormal trio ؊/؊ skeletal myofibers temporally coincided with the onset of secondary myogenesis, and smaller secondary myofibers located adjacent to the primary myofibers were absent. The proliferation of trio ؊/؊ secondary myoblasts appeared normal, suggesting that Trio may regulate secondary myoblast alignment or fusion. trio ؊/؊ embryos also displayed aberrant organization in several regions within the brain, including the hippocampal formation and olfactory bulb. We thus conclude that Trio is essential for late embryonic development, and that Trio functions in fetal skeletal muscle formation and in the organization of neural tissues.gene targeting ͉ embryonic lethality ͉ Rac ͉ mouse development