Obesity is associated with increased risk for infections and poor responses to vaccinations, which may be due to compromised B-cell function. However, there is limited information about the influence of obesity on B-cell function and underlying factors that modulate B-cell responses. Therefore, we studied B-cell cytokine secretion and/or antibody production across obesity models. In obese humans, B-cell IL-6 secretion was lowered and IgM levels were elevated upon ex vivo anti-BCR/TLR9 stimulation. In murine obesity induced by a high fat diet, ex vivo IgM and IgG were elevated with unstimulated B-cells. Furthermore, the high fat diet lowered bone marrow B-cell frequency accompanied by diminished transcripts of early lymphoid commitment markers. Murine B-cell responses were subsequently investigated upon influenza A/Puerto Rico/8/34 infection using a Western diet model in the absence or presence of docosahexaenoic acid (DHA3). DHA, an essential fatty acid with immunomodulatory properties, was tested since its plasma levels are lowered in obesity. Relative to controls, mice consuming the Western diet had diminished antibody titers whereas the Western diet + DHA improved titers. Mechanistically, DHA did not directly target B-cells to elevate antibody levels. Instead, DHA increased the concentration of the downstream specialized pro-resolving lipid mediators (SPMs) 14-HDHA, 17-HDHA, and protectin DX. All three SPMs were found to be effective in elevating murine antibody levels upon influenza infection. Altogether, the results demonstrate that B-cell responses are impaired across human and mouse obesity models and show that essential fatty acid status is a factor influencing humoral immunity, potentially through an SPM-mediated mechanism.

SUMMARY The cranial neural crest (CNC) are multipotent embryonic cells that contribute to craniofacial structures and other cells and tissues of the vertebrate head. During embryogenesis, CNC is induced at the neural plate boundary through the interplay of several major signaling pathways. Here we report that the metalloproteinase activity of ADAM13 is required for early induction of CNC in Xenopus. In both cultured cells and X. tropicalis embryos, membrane-bound Ephrins (Efns) B1 and B2 were identified as substrates for ADAM13. ADAM13 upregulates canonical Wnt signaling and early expression of the transcription factor snail2, whereas EfnB1 inhibits the canonical Wnt pathway and snail2 expression. We propose that by cleaving class B Efns, ADAM13 promotes canonical Wnt signaling and early CNC induction.

A disintegrin and a metalloprotease (ADAM) family members have been implicated in many biological processes. Although it is recognized that recombinant ADAM disintegrin domains can interact with integrins, little is known about ADAM-integrin interactions in cellular context. Here, we tested whether ADAMs can selectively regulate integrinmediated cell migration. ADAMs were expressed in Chinese hamster ovary cells that express defined integrins (␣4␤1, ␣5␤1, or both), and cell migration on full-length fibronectin or on its ␣4␤1 or ␣5␤1 binding fragments was studied. We found that ADAMs inhibit integrin-mediated cell migration in patterns dictated by the integrin binding profiles of their isolated disintegrin domains. ADAM12 inhibited cell migration mediated by the ␣4␤1 but not the ␣5␤1 integrin. ADAM17 had the reciprocal effect; it inhibited ␣5␤1-but not ␣4␤1-mediated cell migration. ADAM19 and ADAM33 inhibited migration mediated by both ␣4␤1 and ␣5␤1 integrins. A point mutation in the ADAM12 disintegrin loop partially reduced the inhibitory effect of ADAM12 on cell migration on the ␣4␤1 binding fragment of fibronectin, whereas mutations that block metalloprotease activity had no effect. Our results indicate that distinct ADAMs can modulate cell migration mediated by specific integrins in a pattern dictated, at least in part, by their disintegrin domains.

A disintegrin and metalloprotease (ADAM) 1 is a family of recently identified cell surface and secreted glycoproteins that possess both proteolytic and adhesive properties (1, 2). Prototypical members of this family are composed of a prodomain, metalloprotease, disintegrin-like, cysteine-rich, EGF-like, transmembrane, and cytoplasmic domains. The metalloprotease domain is homologous to the reprolysins, members of the metazincin superfamily that include the matrix metalloproteases, the astacins, and serralysins (3). Although the ADAMs may serve other proteolytic functions, their role in the ectodomain shedding of specific cell surface proteins has been well documented (4, 5). ADAMs 9 (meltrin-␥), 10 (kuzbian), and 17 (tissue necrosis factor-␣-converting enzyme) have been shown to function in ectodomain shedding of membrane-anchored heparin-binding EGF-like growth factor, amyloid precursor protein, and tissue necrosis factor-␣, respectively (6 -10). These ADAMs and other members of this protein family have also been implicated in the shedding of other proteins such as L-selectin, FasL, and VCAM-1 (11-13). In addition to the proteolytic functions mentioned, several ADAMs have been shown to interact with the integrin family of cell surface receptors. Integrins are a widely distributed superfamily of noncovalent heterodimeric glycoproteins that play a vital role in cellular adhesion, migration, and signal transduction (14, 15). The ADAM disintegrin-like domains are homologous to small non-enzymatic peptides isolated from the venom of snakes that function as antagonists of integrins (16,17). The direct interaction of the snake venom disintegrin peptides with integrins led to the hypothesis that the disintegrin-like domains of ADAMs may function as integrin ligands. The disintegrin-like domains of ADAMs 1-3 expressed on the surface of sperm interact with the integrin ␣ 6 ␤ 1 in association with CD9 and CD98 on the egg surface (18 -23). Recognition of ADAMs 2 and 3 by ␣ 6 ␤ 1 requires the residues DECD located within a region of the disintegrin domain, designated the disintegrin loop, that corresponds to an extended loop in the snake venom peptides that typically contains an RGD sequence required for integrin binding (21-23). Human ADAM 15 contains an RGD sequence within the disintegrin loop region and is recognized by the integrins ␣ v ␤ 3 and ␣ 5 ␤ 1 (24 -26). However, mouse ADAM 15 lacks the RGD sequence found in the human homologue. Both human and mouse ADAM 15 as well as ADAM 12 were shown to be recognized by the integrin ␣ 9 ␤ 1 via residues outside the disintegrin loop (27). Other ADAM disintegrin-like domains reported to bind integrins are ADAM 9, which is recognized by ␣ 6 ␤ 1 and ␣ v ␤ 5 (28, 29), and ADAM 23, which is recognized by ␣ v ␤ 3 (30). * This work was supported by National Institutes of Health Grant AI47314. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section...

The metalloprotease disintegrin cysteine-rich (MDC) proteins are a recently identified family of transmembrane proteins that function in proteolytic processing of cell surface molecules and in cell adhesion. Since lymphocytes must interact with a constantly changing environment, we hypothesized that lymphocytes would express unique MDC proteins. To identify MDC proteins expressed in human lymph node, a polymerase chain reaction-based strategy combined with degenerate oligonucleotide primers was employed. We report here MDC,1 or ADAMs, are a family of transmembrane glycoproteins with a unique domain structure (1, 2). The prototypical MDC protein comprises pro, metalloprotease, disintegrin, cysteine-rich, EGF, transmembrane, and cytoplasmic domains. The metalloprotease domain is homologous to the reprolysins, members of the zinc binding metzincin superfamily that also includes the matrix metalloproteases (MMPs), the astacins, and serralysins (3). The prodomain regulates the activity of the metalloprotease by blocking access to the zinc ion; removal of the prodomain or inactivation of a conserved cysteine thiol group results in a gain of proteolytic activity. The disintegrin domains of MDC proteins are homologous to small nonenzymatic peptides isolated from the venom of snakes. Snake venom disintegrin peptides interfere with platelet aggregation by inhibiting binding of fibrinogen to the integrin ␣ IIb ␤ 3 (4). The functions previously attributed to the individual domains suggests roles for MDC proteins in cell adhesion and the proteolysis of extracellular proteins.The first mammalian MDC proteins identified were the fertilins (5). These proteins function in the attachment and fusion of the sperm and egg during fertilization. A similar cell fusion function for the MDC protein meltrin-␣ (MDC-12) was shown for the formation of multinucleated myotubes (6). These MDC proteins have, in addition to the domains described above, a fusion peptide-like sequence not found in all members of the MDC protein family. However, the interaction of the fertilin disintegrin domain on the sperm surface with the integrin ␣ 6 ␤ 1 on the surface of the egg is also required for membrane adhesion and fusion (7-9). Additional evidence for the functionality of the disintegrin domain comes from studies using recombinantly expressed metargidin (MDC-15) disintegrin domain, which was shown to specifically interact with the integrin