Raf kinase inhibitory protein (RKIP/PEBP1), a member of the phosphatidylethanolamine binding protein family that possesses a conserved ligand-binding pocket, negatively regulates the mammalian mitogen-activated protein kinase (MAPK) signaling cascade. Mutation of a conserved site (P74L) within the pocket leads to a loss or switch in the function of yeast or plant RKIP homologues. However, the mechanism by which the pocket influences RKIP function is unknown. Here we show that the pocket integrates two regulatory signals, phosphorylation and ligand binding, to control RKIP inhibition of Raf-1. RKIP association with Raf-1 is prevented by RKIP phosphorylation at S153. The P74L mutation increases kinase interaction and RKIP phosphorylation, enhancing Raf-1/MAPK signaling. Conversely, ligand binding to the RKIP pocket inhibits kinase interaction and RKIP phosphorylation by a noncompetitive mechanism. Additionally, ligand binding blocks RKIP association with Raf-1. Nuclear magnetic resonance studies reveal that the pocket is highly dynamic, rationalizing its capacity to interact with distinct partners and be involved in allosteric regulation. Our results show that RKIP uses a flexible pocket to integrate ligand binding-and phosphorylation-dependent interactions and to modulate the MAPK signaling pathway. This mechanism is an example of an emerging theme involving the regulation of signaling proteins and their interaction with effectors at the level of protein dynamics.Raf kinase inhibitory protein (RKIP/PEBP1) is a signaling modulator that regulates key signal transduction cascades in mammalian cells (reviewed in reference 16). A negative regulator of mitogen-activated protein kinase (MAPK) signaling (42), RKIP inhibits Raf kinase by binding directly to Raf-1, thereby preventing the phosphorylation and activation of 38). RKIP functions as a regulator of the spindle checkpoint and promotes genomic stability by preventing MAPK from inhibiting Aurora B kinase (10). Consistent with this role, RKIP suppresses lung metastasis by prostate tumor cells in an orthotopic murine model (15). RKIP may be a general metastasis suppressor for solid tumors, since RKIP expression is low or undetectable in prostate and breast tumors, melanoma, hepatocellular carcinoma, and colorectal tumors (1,2,14,15,19,34). Finally, RKIP suppresses NF-B activation (43), inhibits G protein-coupled receptor (GPCR) kinase 2 (GRK2)-mediated downregulation of GPCRs (28), and potentiates the efficacy of chemotherapeutic agents (5). Thus, RKIP regulates three key mammalian signaling pathways involving MAPK, GPCR, and NF-B signaling.RKIP is a member of the phosphatidylethanolamine binding protein (PEBP) family, which extends from bacteria to humans and consists of more than 400 proteins (16, 33). X-ray crystallographic studies have demonstrated that highly conserved sequences cluster around a pocket capable of binding anions, including o-phosphorylethanolamine (PE), acetate, and cacodylate (3,35). This pocket is the only clearly identifiable feature for potent...

A small proportion of avian-exposed humans had evidence of influenza A(H9N2) infection. As the virus has a near global distribution in poultry, it seems likely that present surveillance efforts are missing mild or asymptomatic infections among avian-exposed persons. It seems prudent to closely monitor avian-exposed populations for influenza A(H9N2) infection to provide prepandemic warnings.

BackgroundEquine influenza virus (EIV) epizootics affect 2·1 million Mongolian horses approximately every 10 years and critically impact economy and nomadic livelihood of Mongolia.ObjectivesAn active surveillance program was established in 2011 to monitor influenza viruses circulating among Mongolian horses.MethodsNasal swabs were collected from horses in free‐ranging horse herds in Töv, Khentii, and Dundgovi aimags (provinces) from January to September 2011. Real‐time reversetranscriptase–polymerase chain reaction (rRT‐PCR) was used to determine the presence of influenza A virus. Influenza A‐positive specimens were cultured to amplify virus; viral RNA was extracted, and gene segments were amplified and sequenced by Sanger sequencing.ResultsA total of 745 horses were swabbed; most horses were without clinical signs of illness. In July 2011, reports of influenza‐like illnesses emerged among horses in Mongolia's capital, and subsequently, surveillance efforts were adjusted to swab horses associated with the epizootic. Thirty‐four specimens of rRT‐PCR influenza‐positive virus were collected in May, June, August, and September. Three specimens yielded detectable virus. Gene sequence studies suggested that all three isolates were identical H3N8 viruses. Phylogenetic analyses indicated the strain was very similar to other H3N8 EIVs circulating in central Asia between 2007 and 2008.ConclusionsAs large Mongolian equine herds often seem to suffer from EIV epizootics, it seems prudent to continue such routine equine influenza surveillance. Doing so will provide an early warning system, should novel viruses emerge, help in assessing if EIV is crossing over to infect humans and provide data to assess the likely effectiveness of current EIV vaccines.

These data suggest that people in rural central Thailand may have experienced subclinical avian influenza infections as a result of yet unidentified environmental exposures. Lack of an indoor water source may play a role in transmission.

Because little is known about the ecology of influenza viruses in camels, 460 nasal swab specimens were collected from healthy (no overt illness) Bactrian camels in Mongolia during 2012. One specimen was positive for influenza A virus (A/camel/Mongolia/335/2012[H3N8]), which is phylogenetically related to equine influenza A(H3N8) viruses and probably represents natural horse-to-camel transmission.