Disease relevance of SP-A

• There were no differences in alveolar surfactant pools and the indexes of pulmonary inflammation between the 10 mg/kg dose groups, nor was there any differences observed between either of the groups supplemented with SP-A [1].
• SP-A also stimulates chemotaxis of alveolar macrophages [142], and serves as an opsonin in the phagocytosis of herpes simplex virus [161] Candida tropicalis [138] and various bacteria [137] [2].
• If untreated, the reimplantation response had almost resolved in the 6-h but not in the 20-h ischemia group; pulmonary surfactant, however, continued to be deficient in both ischemia groups (low amounts of surfactant phospholipids and surfactant protein A [SP-A]) [3].

High impact information on SP-A

• Surfactant protein A (SP-A) is crucial for lung function, including tubular myelin formation and lipid uptake by type II pneumocytes [4].
• A recombinant carbohydrate recognition domain (CRD) of human SP-A inhibits the binding of human SP-A to galactosyl ceramide and to galactose- and mannose-bovine serum albumin, indicating that the CRD is directly involved in the binding of SP-A to these ligands [5].
• Surfactant-associated protein-A (SP-A) is a component of pulmonary surfactant that acts as a cytokine through interaction with a cell-surface receptor (SPAR) on lung epithelial cells [6].
• Phosphorylation of IkappaB was minimally affected by SP-A as was NFkappaB gel shift activity [6].
• SP-A regulates important physiological processes including surfactant secretion, gene expression, and protection against apoptosis [6].

Biological context of SP-A

• Assignment of the surfactant protein A gene (SFTPA) to bovine chromosome 28q1.8-->q1.9 by radiation hybrid mapping [7].
• SP-A binding sites on bovine alveolar macrophages [8].
• Chemical reduction or alkylation of SP-A abolished its inhibitory effect on PLA2 activity [9].
• The addition of SP-A produced a concentration-dependent inhibition of T. flavoviridis PLA2 that indicated non-competitive kinetics with Ki 5 micrograms/ml [10].
• A marked sequence homology has been noted between lung surfactant protein A (SP-A) and an inhibitor of phospholipase A2 (PLA2) isolated from the serum of Trimeresurus flavoviridis (Habu snake) [10].

Anatomical context of SP-A

• Human SP-A, unlabeled or labeled with gold particles, was bound to freshly isolated macrophages and analyzed with ELISA or the transmission electron microscope [8].
• We concluded that SP-A is important for maintaining LA forms during surface-area cycling by stabilizing tubular myelin and multilamellar structures [11].
• We suggest that the action of SP-A on PHA-stimulated human PBMC may involve the blocking of a costimulatory signal crucial for in vitro T-cell activation [12].
• We have found that SP-A octadecamers exist in an "opened-bouquet" conformation in the absence of cations and interact with lipid membranes via one or two globular headgroups [13].
• There was little degradation of SP-A by HeLa cells [14].

Associations of SP-A with chemical compounds

• Purified PG (5% wt/wt) restored nearly normal dynamic properties to (DAPL + SP-B/C + SP-A + NL), whereas phosphatidylcholine (PC) (5% wt/wt) had no beneficial effect [15].
• From the fractionated and blotted proteins of the receptor preparation two proteins bound SP-A in a Ca2+-dependent manner, a 40-kDa protein showing mannose dependency and a 210-kDa protein, showing no mannose sensitivity [8].
• SP-A accelerated lipid adsorption but suppressed the final level of cholesterol in the surface [16].
• The effects of surfactant-associated protein A (SP-A) on lipid adsorption to the air-water interface and accumulation of dipalmitoylphosphatidylcholine (DPPC) in the surface region were investigated at 37 degrees C. Dispersions used were bovine pulmonary lipid extract surfactant with or without neutral lipid (NL) [17].
• The major surfactant protein, a 30-36-kDa class of glycoprotein (SP-A), has been isolated from bovine lung lavage and purified by affinity chromatography [18].

Physical interactions of SP-A

• SP-A bound to annexin IV under conditions where contaminated lipid was removed [19].

Regulatory relationships of SP-A

• We studied whether antioxidant-surfactant liposomes increase cellular antioxidant activity in alveolar type II cells and whether this effect is influenced by the presence of surfactant protein A (SP-A) [20].

Other interactions of SP-A

• However, the augmentation of aggregation of the lung lamellar bodies by annexin IV was attenuated when the lamellar bodies were preincubated with polyclonal anti-SP-A antibodies [19].

Analytical, diagnostic and therapeutic context of SP-A

• For isolation of SP-A receptors with homologous SP-A as ligand we isolated SP-A from bovine lung lavage [8].
• SDS-PAGE analysis of the purified SP-A showed a protein of 32-36 kDa [8].
• We have examined the effects of surfactant-associated protein A (SP-A) purified from bovine lavage material on the surface activity of lipid extract surfactant (LES), an organic extract of pulmonary surfactant containing all of the phospholipids and SP-B and SP-C, but lacking SP-A [21].
• The purification procedure yielded 206 mg of high-purity SP-A/kg of porcine lung, as judged by gel filtration, SDS/PAGE and Western blotting [22].
• Gel-filtration experiments confirmed the molecular mass of SP-A in 10 mM NaCl solution [22].

References