1987 Fiscal Year Final Research Report Summary
Metabolism and its regulation of phospholipids and apoproteins of pulmonary surfactant
| Project/Area Number |
61570145
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
Pathological medical chemistry
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| Research Institution | Sapporo Medical College |
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Principal Investigator |
AKINO Toyoaki Professor of Sapporo Medical College, 医学部, 教授 (80045377)
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| Co-Investigator(Kenkyū-buntansha) |
ADACHI Hideki Instructor of Sapporo Medical College, 医学部, 助手 (70191856)
MIZUMOTO Masahiko Instructor of Sapporo Medical College, 医学部, 助手 (60181913)
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| Project Period (FY) |
1986 – 1987
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| Keywords | Pulmonary surfactant / Apoprotein / Dipalmitoyl phosphatidylcholine / Phosphatidylglycerol / リン脂質結合蛋白質 |
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| Research Abstract |
Pulmonary surfactant is a lipoprotein made up of greater than 80% phospholipids, i.e., mainly dipalmitoyl phosphatidylcholine and phosphatidylglycerol, and about 10% apoproteins. The present study was made to elucidate the metabolism and its regulation of the phospholipids and apoproteins in pulmonary surfactant. The new findings obtained are summarized in the following.
1. The 36kD apoprotein(SP36) is the main apoprotein component which has structural heterogeneity due to their different carbohydrate chains. The present study showed the intracellular processing of the SP36 subspecies in alveolar Type II cells; 30kD protein primarily synthesized from mRNA is bound with 7kD carbohydrate chain to form 37kD glycoprotein in microsomes, and the 37 kD protein is processed to the 34kD glycoprotein during the transfer from microsomes to lamellar bodies.
2. The role of SP36 in pulmonary surfactant system was studied. The hydrophobic moiety of SP36 seemed to interact with surfactant phospholipids
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to increase the surface adsorption. However, the interaction may not provide the exceptionally fast surface adsorption that is a characteristic of natural surfactant.
3. Hydrophobic protein of small molecular weight(6kD) has been shown to be functionally more important than SP36 in pulmonary surfactant system. We isolated the SP6 from lipid extract of human bronchoalveolar lavage fluids, and determined the primary structure (57 amino acid sequence) of the human SP6. The great majority of the SP6 molecule was hydrophobic, i.e., lipid-binding domain. The hydrophilic regions were present only at the 6 amino acid residures where appeared to be the antigenic site of the SP6.
4. An acidic phospholipid, phosphatidylglycerol(PG) has been shown to be an essential component of pulmonary surfactant. However, in the fetal lung a predominant acidic phospholipid is not PG but phosphatidylinositol(PI). Thus, it has been suggested that surfactant PG and PI are derived from a same pool of CDP-DG. The present study revealed that the acyl species patterns of PG and PI in the surfactant are distinctly different. This result strongly suggests that surfactant PG and PI are derived from different pools of CDP-DG in alveolar Type II cells. Less
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