An ethanol/ether soluble apoprotein from rat lung surfactant augments liposome uptake by isolated granular pneumocytes.

Abstract

bstract. Ethanol/ether soluble apoproteins, comprising 17% of the total recovered surfactant-associated proteins, were isolated from rat lung surfactant and purified by silicic acid chromatography. The protein that eluted in 4:1 chloroform/methanol accounted for >85% of protein in the ethanol/ether soluble fraction and was termed surfactant apoprotein Et (Apo Et). By sodium dodecyl sulfate polyacrylamide gel electrophoresis, this protein had an apparent molecular weight of -10,500. Apo Et was evaluated for its effect on uptake of synthetic phospholipids in liposomal form by isolated granular pneumocytes (Type II alveolar epithelial cells) in primary culture. Liposomes were prepared to approximate the phospholipid composition of the aveolar surfactant, and uptake was measured by the accumulation of the radioactively labeled dipalmitoyl phosphatidyl choline fraction. The uptake of liposomal phosphatidylcholine by cells incubated for 2 h with Apo Et was increased by 61% over control. Most of the cell-associated phospholipid uptake was resistant to treatment with trypsin, suggesting an increased internalization of liposomal material in the presence of Apo Et. The effect of Apo Et on uptake was concentration and time dependent and was not associated with cell damage,

Ultrastructural Immunohistochemical Localization of Clara Cell Secretory Protein in Pulmonary Epithelium of Rabbits

“…Lopez de Haro et al (24) report that CCSP and uteroglobin must be identical based upon similarities in antibody and progesterone binding. A low molecular weight protein has been reported (25)(26)(27)(28) to be associated with extracellular surfactant in pulmonary lavage effluents, but CCSP appears to be immunochemically different. We have isolated a 6-kDa surfactant protein using the method of Claypool et al (25), and although the molecular weight of this protein is close to that of the Clara cell protein, antisera reactive with the Clara cell protein did not react with the low molecular weight surfactant protein (6).…”

“…A low molecular weight protein has been reported (25)(26)(27)(28) to be associated with extracellular surfactant in pulmonary lavage effluents, but CCSP appears to be immunochemically different. We have isolated a 6-kDa surfactant protein using the method of Claypool et al (25), and although the molecular weight of this protein is close to that of the Clara cell protein, antisera reactive with the Clara cell protein did not react with the low molecular weight surfactant protein (6). In addition, our anti-Clara cell serum did not react with any proteins in the 26 major secretory protein of bronchiolar Clara cells is located primarily in nonciliated cells but could be present to a very small degree in other secretory cells of the pulmonary epithelium, cells such as type II cells and mucous cells.…”

Mixtures of Low Molecular Weight Surfactant Proteins and Dipalmitoyl Phosphatidylcholine Duplicate Effects of Pulmonary Surfactant in Vitro and in Vivo

“…These proteins are markedly hydrophobic (1,5,(7)(8)(9)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23), coisolate with lipids in commonly used organic solvents (1, 4-8, 1 1,13,[15][16][17]20) and may represent monomeric and oligomeric forms of two distinct peptides-SP-B and SP-C (12, 16)-that are derived through proteolytic processing of larger precursor proteins (1,(21)(22)(23)(24). Various reports indicate that SP-B and SP-C, together or separately, augment phospholipid recycling in cell cultures (13,14,19), enhance absorption (1, 5-8, lo), surface spreading and dynamic respreading (6, 7, 9, lo), and surface tension-lowering properties of synthetic phospholipid mixtures or protein-free lipid extracts of natural surfactant in vitro (3-1 1). SP-B and SP-C have also been reported to enhance the abilities of defined lipid mixtures to improve pulmonary compliance in the lungs of premature rabbits (2,4,6,7,9).…”

Immunologic Identification of a Pulmonary Surfactant-Associated Protein of Molecular Weight = 6000 Daltons

“…Gels were stained using a minor modification of the procedures as Sammons et al (25) in which 5% acetic acid was used to control background staining following a 5-to 10-minute Na z C0 3 color development step. Low molecular weight protein markers were obtained from BRL Incorporated, Bethesda, MD: trypsin inhibitor (6,200), lysozyme (14,000) ,B-Iactalbumin (18,400), achymotrypsin (25,700), and ovalbumin (43,000). Radiolabeled protein markers were obtained from Amersham Inc., Arlington, IL.…”

“…Mam~~ian pulmon~ry surfactant is composed primarily of phospholIpIds~nd ass?cIat~d proteins, Two major protein groups h~ve been prevIOusly IdentIfied: a surfactant-associated glycoprotem of 3~-40,000 daltons first described by King and Clements (1), hereI~called .SAP-35 and smaller molecular weight proteins det~cted m a v~net~of mammalian surfactants (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12). ClarificatIon of the IdentIty and nature of the various surfactantassociated proteins has been incomplete.…”