Highlights d Mechanical skin injury promotes intestinal mast-cell expansion d Intestinal mast-cell expansion requires skin-derived IL-33 and gut-derived IL-25 d Intestinal mast-cell expansion requires ILC2 activation by IL-33 and IL-25 d ILC2-derived IL-4 and IL-13 directly cause intestinal mast-cell expansion

Background Cutaneous exposure to food allergens predisposes to food allergy, which is commonly associated with atopic dermatitis (AD). The levels of the epithelial cytokine IL-33 are increased in skin lesions and serum of AD patients. Mast cells (MC) play a critical role in food anaphylaxis and express the IL-33 receptor ST2. The role of IL-33 in MC-dependent food anaphylaxis is unknown. Objective To determine the role and mechanism of action of IL-33 in food anaphylaxis in a model of IgE-dependent food anaphylaxis elicited by oral challenge of epicutaneously (EC)-sensitized mice. Methods WT, ST2-deficient and MC-deficient KitW-sh/W-sh mice were EC sensitized with ovalbumin (OVA) then challenged orally with OVA. Body temperature was measured by telemetry, Il33 mRNA by qPCR, and IL-33, OVA-specific IgE and mouse mast cell protease 1 (mMCP-1) by ELISA. Bone marrow-derived MCs (BMMCs) degranulation was assessed by flow cytometry. Results Il33 mRNA expression was upregulated in tape-stripped mouse skin and scratched human skin. Tape stripping caused local and systemic IL-33 release in mice. ST2 deficiency, as well as ST2 blockade prior to oral challenge, significantly reduced the severity of oral anaphylaxis without affecting the systemic Th2 response to the allergen. Oral anaphylaxis was abrogated in KitW-sh/W-sh mice, and restored by reconstitution with WT, but not ST2-deficient, BMMCs. IL-33 significantly enhanced IgE-mediated degranulation of BMMCs in vitro. Conclusion IL-33 is released following mechanical skin injury, enhances IgE-mediated MC degranulation, and promotes oral anaphylaxis following EC sensitization by targeting MCs. IL-33 neutralization may be useful in treating food anaphylaxis in AD patients.

Spectrins, components of the membrane skeleton, are implicated in various cellular functions. Understanding the diversity of these functions requires better characterization of the interacting domains of spectrins, such as the SH3 domain. Yeast two-hybrid screening of a kidney cDNA library revealed that the SH3 domain of ␣II-spectrin binds specifically isoform A of low-molecular-weight phosphotyrosine phosphatase (LMW-PTP). The ␣II-spectrin SH3 domain does not interact with LMW-PTP B or C nor does LMW-PTP A interact with the ␣I-spectrin SH3 domain. The interaction of spectrin with LMW-PTP A led us to look for a tyrosinephosphorylated residue in ␣II-spectrin. Western blotting showed that ␣II-spectrin is tyrosine phosphorylated in vivo. Using mutagenesis on recombinant peptides, we identified the residue Y1176 located in the calpain cleavage site of ␣II-spectrin, near the SH3 domain, as an in vitro substrate for Src kinase and LMW-PTP A. This Y1176 residue is also an in vivo target for kinases and phosphatases in COS cells. Phosphorylation of this residue decreases spectrin sensitivity to calpain in vitro. Similarly, the presence of phosphatase inhibitors in cell culture is associated with the absence of spectrin cleavage products. This suggests that the Y1176 phosphorylation state could modulate spectrin cleavage by calpain and may play an important role during membrane skeleton remodeling.First identified at the intracellular surface of the erythrocyte plasma membrane, spectrins (Sp) are now known to be the central components of the membrane skeleton, a ubiquitous and complex spectrin-actin scaffold located under the lipid bilayer of metazoan animal cells (for review, see references 4 and 21). Numerous studies on red cells, particularly those in hereditary hemolytic anemia, have clearly established the organization of the erythrocyte skeleton and its importance in maintaining erythrocyte shape, stability, and deformability. Spectrins are giant extended flexible molecules composed of two subunits (␣I and ␤I in red cells) which intertwine to form ␣␤ heterodimers. Spectrin exists as elongated tetramers resulting from self-association of ␣␤ heterodimers. Sp tetramers constitute the filaments of the lattice, the nodes of which are crossed-linked by short actin filaments. This spectrin-based skeleton is bound to various transmembrane proteins through two connecting proteins, ankyrin and protein 4.1.In nonerythroid mammal cells, ␣ (␣I and ␣II) and ␤ (␤I to ␤V) chains are encoded by two and five genes, respectively, each of these genes producing several isoforms by alternative splicing. Despite this diversity, all Sp chains present the same structural organization mainly made up of a succession of triple-helical repeat units, 22 for ␣ chains and 17 for ␤ chains except ␤V, which has 30 repeats. These units are characteristic of spectrin family members. They are about 106 amino acids long and folded in a coiled-coil structure made up of three helices (A, B, and C). Beside these repeat units, spectrin isoforms can also con...