Severe impairment of interleukin-1 and Toll-like receptor signalling in mice lacking IRAK-4

Toll-like receptors (TLRs), which recognize pathogen-associated molecular patterns, and members of the pro-inflammatory interleukin-1 receptor (IL-1R) family, share homologies in their cytoplasmic domains called Toll/IL-1R/plant R gene homology (TIR) domains. Intracellular signalling mechanisms mediated by TIRs are similar, with MyD88 (refs 5-8) and TRAF6 (refs 9, 10) having critical roles. Signal transduction between MyD88 and TRAF6 is known to involve the serine-threonine kinase IL-1 receptor-associated kinase 1 (IRAK-1) and two homologous proteins, IRAK-2 (ref. 12) and IRAK-M. However, the physiological functions of the IRAK molecules remain unclear, and gene-targeting studies have shown that IRAK-1 is only partially required for IL-1R and TLR signalling. Here we show by gene-targeting that IRAK-4, an IRAK molecule closely related to the Drosophila Pelle protein, is indispensable for the responses of animals and cultured cells to IL-1 and ligands that stimulate various TLRs. IRAK-4-deficient animals are completely resistant to a lethal dose of lipopolysaccharide (LPS). In addition, animals lacking IRAK-4 are severely impaired in their responses to viral and bacterial challenges. Our results indicate that IRAK-4 has an essential role in innate immunity.     

Neuronal control of brain microvessel function

Cerebral capillary endothelium forms a barrier limiting and controlling the movement of ions and solutes between blood and brain. Recent anatomical, physiological and biochemical studies have suggested the possibility that capillary function may be directly controlled by neuronal structures. Alterations in neuronal systems involved in the regulation of microcirculation may account for microvascular dysfunctions which occur in different pathologic conditions.     

Protein-based peptide-bond formation by aminoacyl-tRNA protein transferase

Eubacterial leucyl/phenylalanyl-tRNA protein transferase (LF-transferase) catalyses peptide-bond formation by using Leu-tRNA(Leu) (or Phe-tRNA(Phe)) and an amino-terminal Arg (or Lys) of a protein, as donor and acceptor substrates, respectively. However, the catalytic mechanism of peptide-bond formation by LF-transferase remained obscure. Here we determine the structures of complexes of LF-transferase and phenylalanyl adenosine, with and without a short peptide bearing an N-terminal Arg. Combining the two separate structures into one structure as well as mutation studies reveal the mechanism for peptide-bond formation by LF-transferase. The electron relay from Asp 186 to Gln 188 helps Gln 188 to attract a proton from the alpha-amino group of the N-terminal Arg of the acceptor peptide. This generates the attacking nucleophile for the carbonyl carbon of the aminoacyl bond of the aminoacyl-tRNA, thus facilitating peptide-bond formation. The protein-based mechanism for peptide-bond formation by LF-transferase is similar to the reverse reaction of the acylation step observed in the peptide hydrolysis reaction by serine proteases.     

Enhancement of chilling tolerance of a cyanobacterium by genetic manipulation of fatty acid desaturation

The sensitivity (or tolerance) of plants to chilling determines their choice of natural habitat and also limits the worldwide production of crops. Although the molecular mechanism for chilling sensitivity has long been debated, no definitive conclusion has so far been reached about its nature. A probable hypothesis, however, is that chilling injury is initiated by phase transition of lipids of cellular membranes, as demonstrated for cyanobacteria, which serve as a model system for the plant cells. Because the phase transition temperature depends on the degree of unsaturation of fatty acids of the membrane lipids, it is predicted that the chilling tolerance of plants can be altered by genetically manipulating fatty-acid desaturation by introducing double bonds into fatty acids of membrane lipids. Here we report the cloning of a gene for the plant-type desaturation (termed desA). The introduction of this gene from a chilling-resistant cyanobacterium, Synechocystis PCC6803, into a chilling-sensitive cyanobacterium, Anacystis nidulans, increases the tolerance of the recipient to low temperature.     

Low-molecular-weight enzyme inhibitors suppress the development of experimental allergic encephalomyelitis

We tested the activity of low-molecular-weight enzyme inhibitors with immunomodifying actions on the suppression of experimental allergic encephalomyelitis (EAE). Of the agents tested the inhibitors of alkaline phosphatase, aminopeptidase B and esterase gave significant protection against the clinical expression of EAE in guinea pigs.     

Sequence and expression of a frog brain complementary DNA encoding a kainate-binding protein

Excitatory amino acids (EAAs) are important neurotransmitters in the vertebrate central nervous system. Electrophysiological and ligand-binding studies indicate that at least three different receptor subtypes for EAAs exist--N-methyl-D-aspartate, kainate and quisqualate receptor subtypes--on the basis of the preferred agonist of the receptors. We recently purified a kainate-binding protein (KBP) from frog (Rana pipiens berlandieri) brain by domoic acid (a high-affinity kainate analogue) affinity chromatography, and showed that the kainate-binding activity was associated with a protein of relative molecular mass 48,000 (Mr 48 K). The pharmacological properties and the anatomical distribution of KBP were consistent with those of a kainate receptor-ionophore complex. We have now isolated a complementary DNA encoding KBP of Mr 48 K. The deduced amino-acid sequence of the KBP has similar hydrophobic profiles to those found in other ligand-gated ion channel subunits, and shows some amino-acid sequence similarities to the corresponding regions of brain nicotinic acetylcholine receptor subunits. Localization of the KBP messenger RNAs by in situ hybridization histochemistry is compatible with the results of immunohistochemistry and receptor autoradiography studies. COS-7 cells transfected with the cDNA encoding the KBP show high-affinity kainate-binding activity with pharmacological properties similar to those of the biochemically purified KBP. These results provide the first molecular characterization of an EAA-binding site and raise the possibility that the KBP cDNA encodes a ligand-binding subunit of a kainate receptor-ionophore complex.     

Primary structure and functional expression of the inositol 1,4,5-trisphosphate-binding protein P400

Cloning and expression of functional P400 protein from cerebellar Purkinje neurons shows that this protein is a receptor for inositol 1,4,5-trisphosphate, a second messenger that mediates the release of intracellular calcium.     

Entrainment of human circadian rhythms by artificial bright light cycles

Summary Artificial bright light cycles (LD 816) of about 5000 lux during the light period were applied to two subjects in a temporal isolation unit, who had shown free-running circadian rhythms in sleep-wakefulness and rectal temperature. The circadian rhythms were successfully entrained by the artificial light cycle, but the phase relation of the rhythms to the light cycle was substantially different between the two subjects. The result indicated that the artificial bright lights are able to reset human circadian rhythms.     

Stargazin modulates AMPA receptor gating and trafficking by distinct domains

AMPA (alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid) receptors mediate fast excitatory synaptic transmission in the brain. These ion channels rapidly deactivate and desensitize, which determine the time course of synaptic transmission. Here, we find that the AMPA receptor interacting protein, stargazin, not only mediates AMPA receptor trafficking but also shapes synaptic responses by slowing channel deactivation and desensitization. The cytoplasmic tail of stargazin determines receptor trafficking, whereas the ectodomain controls channel properties. Stargazin alters AMPA receptor kinetics by increasing the rate of channel opening. Disrupting the interaction of stargazin ectodomain with hippocampal AMPA receptors alters the amplitude and shape of synaptic responses, establishing a crucial function for stargazin in controlling the efficacy of synaptic transmission in the brain.