1998 Fiscal Year Final Research Report Summary
Host defense mechanism and modulation of lipid metabolism by pulmonary surfactant proteins
| Project/Area Number |
09670159
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Pathological medical chemistry
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| Research Institution | Sapporo Medical University |
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Principal Investigator |
KUROKI Yoshio Sapporo Medical University, School of Medicine, Professor, 医学部, 教授 (70161784)
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| Co-Investigator(Kenkyū-buntansha) |
SANO Hitomi Sapporo Medical University, School of Medicine, Research Associate, 医学部, 助手 (80295344)
SOHMA Hitoshi Sapporo Medical University, School of Medicine, Assistant Professor, 医学部, 講師 (70226702)
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| Project Period (FY) |
1997 – 1998
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| Keywords | pulmonary surfactant / SP-A / SP-D / mannose-binding protein / collectin / lipopolysaccharides / CD14 / TNFalpha |
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| Research Abstract |
1. Pulmonary surfactant proteins A and D (SP-A and SP-D) and mannose-binding protein A(MBP-A) are collectins in the C-type lectin superfamily. These collectins exhibit unique lipid binding properties. The structure-function relationship was investigated by using SP-ASP-D chimeras, It was found that the SP-A region of Glu^<195>- Phe^<228> is required for lipid and type II cell interactions and that the SP-D region of Cys^<261>-Phe^<355> is required for optimal lipid interactions.
Monoclonal antibodies (mAbs PElO and PC6) that recognize human SP-A inhibit the interactions of SP-A with lipids and alveolar type II cells. We mapped the epitopes for antihuman SP-A mAbs by a phage display peptide library. Phage selected by mAbs displayed the consensus peptide sequences that are nearly identical to ^<184>TPVNYTNWYRG^<194> of human SP-A.Chimeric proteins were generated in which the rat SP-A region Thr^<174>-Gly^<194> was replaced with the MBP-A region Thr^<164>-Asp^<184> (rat ama4, respectively)
… More
. Rat ama4 bound to an affinity matrix on mannose-sepharose but lost all of the SP-A functions except carbohydrate binding and Ca^<2+> independent GalCer binding. Strikingly, the rat ama4 chimera acquired the PI binding property that MBP-A exhibits. This study demonstrates that the amino acid residues 174-194 of SP-A and the corresponding region of MBP-A are critical for SP-A-type II cell interaction and Ca^<2+>-dependent lipid binding of collectins.
2. Pulmonary surfactant protein A (SP-A) plays an important part in antibody independent host defense mechanisms of the lung. SP-A bound to rough forms but not to smooth forms of LPS.When U937 cells and rat alveolar macrophages were preincubated with SP-A ; smooth LPS failed to induce TNFalpha secretion while rough LPS-induced TNFalpha secretion was modestly increased. Western blot analysis revealed that CD14 was one of the SP-A-binding proteins isolated from solubilized U937 cells. In addition, SP-A directly bound to recombinant soluble CD14 (rsCDl4). When rsCDl4 was preincubated with SP-A, the binding of rsCDl4 to smooth LPS was significantly reduced but the association of rsCDl4 with rough LPS was augmented. These results demonstrate the different actions of SP-A upon distinct serotypes of LPS, and indicate that the direct interaction of SP-A with CD14 constitutes a likely mechanism by which SP-A modulates LPS-elicited cellular responses. Less
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