Diverse Functions of Pulmonary Collectins in Host Defense of the Lung

Pulmonary surfactant is a mixture of lipids and proteins that covers alveolar surfaces and keeps alveoli from collapsing. Four specific proteins have been identified in surfactant. Among them, two C-type lectins, surfactant proteins A and D (SP-A and SP-D), are known to be implicated in host defense and regulation of inflammatory responses of the lung. These host defense lectins are structurally characterized by N-terminal collagen-like domains and lectin domains and are called pulmonary collectins. They prevent dissemination of infectious microbes by their biological activities including agglutination and growth inhibition. They also promote clearance of microbes by enhancing phagocytosis in macrophages. In addition, they interact with the other pattern-recognition molecules, including Toll-like receptors (TLRs) and TLR-associated molecules, CD14 and MD-2, and regulate inflammatory responses. Furthermore, recent studies have demonstrated that these collectins modulate functions of neutrophil-derived innate immune molecules by interacting with them. These findings indicate that pulmonary collectins play critical roles in host defense of the lung

A nested leucine rich repeat (LRR) domain: The precursor of LRRs is a ten or eleven residue motif

<p>Abstract</p> <p>Background</p> <p>Leucine rich repeats (LRRs) are present in over 60,000 proteins that have been identified in viruses, bacteria, archae, and eukaryotes. All known structures of repeated LRRs adopt an arc shape. Most LRRs are 20-30 residues long. All LRRs contain LxxLxLxxNxL, in which "L" is Leu, Ile, Val, or Phe and "N" is Asn, Thr, Ser, or Cys and "x" is any amino acid. Seven classes of LRRs have been identified. However, other LRR classes remains to be characterized. The evolution of LRRs is not well understood.</p> <p>Results</p> <p>Here we describe a novel LRR domain, or nested repeat observed in 134 proteins from 54 bacterial species. This novel LRR domain has 21 residues with the consensus sequence of LxxLxLxxNxLxxLDLxx(N/L/Q/x)xx or LxxLxCxxNxLxxLDLxx(N/L/x)xx. This LRR domain is characterized by a nested periodicity; it consists of alternating 10- and 11- residues units of LxxLxLxxNx(x/-). We call it "IRREKO" LRR, since the Japanese word for "nested" is "IRREKO". The first unit of the "IRREKO" LRR domain is frequently occupied by an "SDS22-like" LRR with the consensus of LxxLxLxxNxLxxLxxLxxLxx or a "Bacterial" LRR with the consensus of LxxLxLxxNxLxxLPxLPxx. In some proteins an "SDS22-like" LRR intervenes between "IRREKO" LRRs.</p> <p>Conclusion</p> <p>Proteins having "IRREKO" LRR domain are almost exclusively found in bacteria. It is suggested that IRREKO@LRR evolved from a common ancestor with "SDS22-like" and "Bacterial" classes and that the ancestor of IRREKO@LRR is 10 or 11 residues of LxxLxLxxNx(x/-). The "IRREKO" LRR is predicted to adopt an arc shape with smaller curvature in which β-strands are formed on both concave and convex surfaces.</p

Comparative sequence analysis of leucine-rich repeats (LRRs) within vertebrate toll-like receptors

<p>Abstract</p> <p>Background</p> <p>Toll-like receptors (TLRs) play a central role in innate immunity. TLRs are membrane glycoproteins and contain leucine rich repeat (LRR) motif in the ectodomain. TLRs recognize and respond to molecules such as lipopolysaccharide, peptidoglycan, flagellin, and RNA from bacteria or viruses. The LRR domains in TLRs have been inferred to be responsible for molecular recognition. All LRRs include the highly conserved segment, LxxLxLxxNxL, in which "L" is Leu, Ile, Val, or Phe and "N" is Asn, Thr, Ser, or Cys and "x" is any amino acid. There are seven classes of LRRs including "typical" ("<b><it>T</it></b>") and "bacterial" ("<b><it>S</it></b>"). All known domain structures adopt an arc or horseshoe shape. Vertebrate TLRs form six major families. The repeat numbers of LRRs and their "phasing" in TLRs differ with isoforms and species; they are aligned differently in various databases. We identified and aligned LRRs in TLRs by a new method described here.</p> <p>Results</p> <p>The new method utilizes known LRR structures to recognize and align new LRR motifs in TLRs and incorporates multiple sequence alignments and secondary structure predictions. TLRs from thirty-four vertebrate were analyzed. The repeat numbers of the LRRs ranges from 16 to 28. The LRRs found in TLRs frequently consists of LxxLxLxxNxLxxLxxxxF/LxxLxx ("<b><it>T</it></b>") and sometimes short motifs including LxxLxLxxNxLxxLPx(x)LPxx ("<b>S</b>"). The <it>TLR7 </it>family (TLR7, TLR8, and TLR9) contain 27 LRRs. The LRRs at the N-terminal part have a super-motif of <b><it>STT </it></b>with about 80 residues. The super-repeat is represented by <b><it>STTSTTSTT </it></b>or <b><it>_TTSTTSTT</it></b>. The LRRs in TLRs form one or two horseshoe domains and are mostly flanked by two cysteine clusters including two or four cysteine residue.</p> <p>Conclusion</p> <p>Each of the six major TLR families is characterized by their constituent LRR motifs, their repeat numbers, and their patterns of cysteine clusters. The central parts of the <it>TLR1 </it>and <it>TLR7 </it>families and of TLR4 have more irregular or longer LRR motifs. These central parts are inferred to play a key role in the structure and/or function of their TLRs. Furthermore, the super-repeat in the <it>TLR7 </it>family suggests strongly that "bacterial" and "typical" LRRs evolved from a common precursor.</p

A novel type of binding specificity to phospholipids for rat mannose-binding proteins isolated from serum and liver

AbstractMannose-binding protein (MBP) belongs to the collectin subgroup of C-type lectins with specificity for mannose and N-acetylglucosamine sugars. We investigated whether rat MBPs isolated from serum (S-MBP) and liver (L-MBP) interact with phospholipids using antibody against each MBP. Both S- and L-MBPs bound to phosphatidylinositol coated onto microtiter wells in a concentration- and a Ca2+-dependent manner. L-MBP also bound to phosphatidylglycerol and weakly to phosphatidylserine. MBPs interacted with liposomes composed of these lipids. S- and L-MBPs bound to phosphatidylinositol 4-monophosphate. L-MBP also bound to cardiolipin. These results provide evidence for a novel type of ligand binding specificity for MBPs, and raise the possibility that phospholipids are ligands for collectins

Expression of Pulmonary Surfactant Protein A (SP-A) in Lung Cancer Lines

Pulmonary surfactant protein A (SP-A) is known to be a major phospholipid- associated 28-35 kDa glycoprotein in pulmonary surfactant, which is specific to the lung. Immunohistochemically, SP-A expression in the tumor tissues is demonstrated in approximately half of the cases of primary lung adenocarcinoma, but not in other histologic types of lung cancer nor in metas-tatic lung tumors. In the present study, to evaluate SP-A synthesis and secre-tion from lung cancer lines, SP-A content in culture supernatants was measured with SP-A enzyme linked immunosorbent assay and SP-A expression in tumor cells was analyzed immunohistochemically employing 10 lung adenocarcinoma lines, 3 lung epidermoid carcinoma lines and 5 lung small cell carcinoma lines. In only one line, LC117 out of 10 lung adenocarcinoma lines, SP-A content was high in the culture supernatant and SP-A was expressed in tumor cells, while other 9 lung adenocarcinoma lines, all lung epidermoid carcinoma lines and all lung small cell lines each exhibited a trace SP-A level in the culture supernatant and tumor cells alone failed to express SP-A. The present result indicated that in almost all lung adenocarcinoma lines function of SP-A synthesis may be lost during establishment of cancer lines

Deconstructing the traditional Japanese medicine “Kampo”: compounds, metabolites and pharmacological profile of maoto, a remedy for flu-like symptoms

Pharmacological activities of the traditional Japanese herbal medicine (Kampo) are putatively mediated by complex interactions between multiple herbal compounds and host factors, which are difficult to characterize via the reductive approach of purifying major bioactive compounds and elucidating their mechanisms by conventional pharmacology. Here, we performed comprehensive compound, pharmacological and metabolomic analyses of maoto, a pharmaceutical-grade Kampo prescribed for flu-like symptoms, in normal and polyI:C-injected rats, the latter suffering from acute inflammation via Toll-like receptor 3 activation. In total, 352 chemical composition-determined compounds (CCDs) were detected in maoto extract by mass spectrometric analysis. After maoto treatment, 113 CCDs were newly detected in rat plasma. Of these CCDs, 19 were present in maoto extract, while 94 were presumed to be metabolites generated from maoto compounds or endogenous substances such as phospholipids. At the phenotypic level, maoto ameliorated the polyI:C-induced decrease in locomotor activity and body weight; however, body weight was not affected by individual maoto components in isolation. In accordance with symptom relief, maoto suppressed TNF-α and IL-1β, increased IL-10, and altered endogenous metabolites related to sympathetic activation and energy expenditure. Furthermore, maoto decreased inflammatory prostaglandins and leukotrienes, and increased anti-inflammatory eicosapentaenoic acid and hydroxyl-eicosapentaenoic acids, suggesting that it has differential effects on eicosanoid metabolic pathways involving cyclooxygenases, lipoxygenases and cytochrome P450s. Collectively, these data indicate that extensive profiling of compounds, metabolites and pharmacological phenotypes is essential for elucidating the mechanisms of herbal medicines, whose vast array of constituents induce a wide range of changes in xenobiotic and endogenous metabolism