Oxytocin (OXT) is an important neurohypophyseal hormone that influences wide spectrum of reproductive and social processes. Eutherian mammals possess a highly conserved sequence of OXT (Cys-Tyr-Ile-Gln-Asn-Cys-Pro-Leu-Gly). However, in this study, we sequenced the coding region for OXT in 22 species covering all New World monkeys (NWM) genera and clades, and characterize five OXT variants, including consensus mammalian Leu8-OXT, major variant Pro8-OXT, and three previously unreported variants: Ala8-OXT, Thr8-OXT, and Phe2-OXT. Pro8-OXT shows clear structural and physicochemical differences from Leu8-OXT. We report multiple predicted amino acid substitutions in the G protein-coupled OXT receptor (OXTR), especially in the critical N-terminus, which is crucial for OXT recognition and binding. Genera with same Pro8-OXT tend to cluster together on a phylogenetic tree based on OXTR sequence, and we demonstrate significant coevolution between OXT and OXTR. NWM species are characterized by high incidence of social monogamy, and we document an association between OXTR phylogeny and social monogamy. Our results demonstrate remarkable genetic diversity in the NWM OXT/OXTR system, which can provide a foundation for molecular, pharmacological, and behavioral studies of the role of OXT signaling in regulating complex social phenotypes.

TLR4 signaling is critical for providing effective immune protection but must be tightly controlled to avoid inflammation-induced pathology. Previously, we reported extensive and direct interactions between Toll-like receptor and Siglec families of Pattern Recognition Receptors. Here, we examined the biological significance of this interaction during infection. We show that Siglec-E is required for E. coli-induced endocytosis of TLR4. Siglec-E-deficient dendritic cells infected with E. coli fail to internalize TLR4, leading to sustained TLR4 on cell surface and activation of NF-κB and MAP kinase p38, thus resulting in high levels of TNF-α and IL-6, compared with wild-type dendritic cells. In contrast to the signaling events occurring at the plasma membrane, as a result of the inability of internalization of TLR4, Siglec-E-deficient dendritic cells were also defective for TRIF-mediated IFN-β production in response to E. coli infection. Furthermore, we found that accumulation of ubiquitinated-TLR4 and binding of E3 ubiquitin ligase Triad3A to TLR4 was significantly increased in bone marrow-derived dendritic cells from wild-type mice but not from Siglec-E-deficient mice after E. coli infection. This represents a newly discovered mechanism that regulates the signaling of TLR4 during E. coli infection.

Sepsis is one of the leading causes of death worldwide. Although the prevailing theory for the sepsis syndrome is a condition of uncontrolled inflammation in response to infection, sepsis is increasingly being recognized as an immunosuppressive state known as endotoxin tolerance. We found sialylation of cell surface was significantly increased on LPS-induced tolerant cells; knockdown of Neu1 in macrophage cell line RAW 264.7 cells resulted in enhanced LPS-induced tolerance, whereas overexpression of Neu1 or treatment with sialidase abrogated LPS-induced tolerance, as defined by measuring TNF-␣ levels in the culture supernatants. We also found that the expression of Siglec-1 (a member of sialic acid-binding Ig (I)-like lectin family members, the predominant sialic acid-binding proteins on cell surface) was specifically up-regulated in endotoxin tolerant cells and the induction of Siglec-1 suppresses the innate immune response by promoting TGF-␤1 production. The enhanced TGF-␤1 production by Siglec-1 was significantly attenuated by spleen tyrosine kinase (Syk) inhibitor. Knockdown of siglec-1 in RAW 264.7 cells resulted in inhibiting the production of TGF-␤1 by ubiquitin-dependent degradation of Syk. Mechanistically, Siglec-1 associates with adaptor protein DNAX-activation protein of 12 kDa (DAP12) and transduces a signal to Syk to control the production of TGF-␤1 in endotoxin tolerance. Thus, Siglec-1 plays an important role in the development of endotoxin tolerance and targeted manipulation of this process could lead to a new therapeutic opportunity for patients with sepsis.Sepsis is generally defined as a systemic inflammatory response syndrome in response to infection. Sepsis can be potentially life threatening; of more than 1 million Americans who are diagnosed with severe sepsis every year, between 28 and 50% will die from this disease (1, 2). It is well-recognized that patients with sepsis are often immune suppressed, a state of reduced responsiveness to endotoxin known as endotoxin tolerance, deaths in this immunosuppressive phase are typically due to failure to control the secondary infections (3-5). The molecular mechanisms underlying this endotoxin tolerance phenomenon is poorly understood.Sialic acids are a family of nine-carbon acidic monosaccharides and are involved in immune response, such as host-pathogen recognition, migration, and antigen presentation. Mounting experimental evidence suggests that the presence of sialic acid residue act as a marker of self in the immune system, as such residues are absent from most microbes (6). Indeed, host cells can be lysed by immune cytotoxic effector mechanisms after extensive desialylation, an observation that demonstrates the significant role played by cell surface sialic acids in the selfrecognition process (7). In addition, normal human serum contains natural antibodies to sialidase-treated red blood cells (7-9), lymphocytes (10), and thymocytes (7). Recently, Meesmann et al. showed that desialylation acted as an "eat me" signal and caused an enhanced upt...

The neurohypophysial hormone arginine vasopressin (AVP) plays important roles in fluid regulation and vascular resistance. Differences in AVP receptor expression, particularly mediated through variation in the noncoding promoter region of the primary receptor for AVP (AVPR1a), may play a role in social phenotypes, particularly social monogamy, in rodents and humans. Among primates, social monogamy is rare, but is common among New World monkeys (NWM). AVP is a nonapeptide and generally conserved among eutherian mammals, although a recent paper demonstrated that some NWM species possess a novel form of the related neuropeptide hormone, oxytocin. We therefore characterized variation in the AVP and AVPR1a genes in 22 species representing every genus in the three major platyrrhine families (Cebidae, Atelidae and Pitheciidae). For AVP, a total of 16 synonymous substitutions were detected in 15 NWM species. No non-synonymous substitutions were noted, hence, AVP is conserved in NWM. By contrast, relative to the human AVPR1a, 66 predicted amino acids (AA) substitutions were identified in NWM. The AVPR1a N-terminus (ligand binding domain), third intracellular (G-protein binding domain), and C-terminus were variable among species. Complex evolution of AVPR1a is also apparent in NWM. A molecular phylogenetic tree inferred from AVPR1a coding sequences revealed some consensus taxonomic separation by families, but also a mixed group composed of genera from all three families. The overall dN/dS ratio of AVPR1a was 0.11, but signals of positive selection in distinct AVPR1a regions were observed, including the N-terminus, in which we identified six potential positive selection sites. AA substitutions at positions 241, 319, 399 and 409 occurred uniquely in marmosets and tamarins. Our results enhance the appreciation of genetic diversity in the mammalian AVP/AVPR1a system, and set the stage for molecular modeling of the neurohypophyseal hormones and social behavior in primates.