AJP - Lung Cellular and Molecular Physiology, Vol 262, Issue 4 437-L445, Copyright © 1992 by American Physiological Society

ARTICLES

Expression and transport of rabbit surfactant protein A in COS-1 cells

J. L. Alcorn, Q. Chen, V. Boggaram and C. R. Mendelson
Department of Biochemistry, Cecil H. and Ida Green Center for Reproductive Biology Sciences, University of Texas Southwestern Medical Center, Dallas 75235.

SV40-transformed green monkey kidney (COS-1) cells were transfected with expression plasmids that contained either the structural gene or cDNA for surfactant protein A (SP-A), a major protein of rabbit lung surfactant. The transfected COS-1 cells synthesized several isoforms of SP-A that were found to be less acidic than those produced in rabbit lung tissue. SP-A species with apparent molecular weight (M(r)) approximately equal to 29,000-33,000 were detected in the transfected cells, whereas glycosylated forms with apparent M(r) approximately equal to 33,000-38,000 were detectable only in the culture medium. Analysis of transfected cells by indirect immunofluorescence revealed that SP-A was localized in punctate bodies throughout the cytoplasm. Expressed SP-A was not detectable on the cell surface nor was there evidence that secreted SP-A was endocytosed by COS-1 cells. After subcellular fractionation of the transfected COS-1 cells, SP-A was found to be localized predominantly in the 5,000- and 18,000-g pellet fractions; little or no immunoreactive SP-A was detectable in cytosolic fractions. Treatment of transfected cells with the glycosylation inhibitor tunicamycin prevented secretion of SP-A into the medium, suggesting a role of glycosylation in secretion of SP-A. On the other hand, treatment of transfected cells with inhibitors of proline hydroxylation, which may cause destabilization of the collagen-like domain of SP-A, reduced but did not prevent secretion of SP-A into the culture medium.(ABSTRACT TRUNCATED AT 250 WORDS)

This article has been cited by other articles:

				J. L. Alcorn, M. E. Smith, J. F. Smith, L. R. Margraf, and C. R. Mendelson Primary Cell Culture of Human Type II Pneumonocytes: Maintenance of a Differentiated Phenotype and Transfection with Recombinant Adenoviruses Am. J. Respir. Cell Mol. Biol., December 1, 1997; 17(6): 672 - 682. [Abstract] [Full Text]

				P. Brown-Augsburger, D. Chang, K. Rust, and E. C. Crouch Biosynthesis of Surfactant Protein D. CONTRIBUTIONS OF CONSERVED NH2-TERMINAL CYSTEINE RESIDUES AND COLLAGEN HELIX FORMATION TO ASSEMBLY AND SECRETION J. Biol. Chem., August 2, 1996; 271(31): 18912 - 18919. [Abstract] [Full Text] [PDF]