In:
American Journal of Physiology-Lung Cellular and Molecular Physiology, American Physiological Society, Vol. 262, No. 4 ( 1992-04-01), p. L437-L445
Abstract:
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)
Type of Medium:
Online Resource
ISSN:
1040-0605
,
1522-1504
DOI:
10.1152/ajplung.1992.262.4.L437
Language:
English
Publisher:
American Physiological Society
Publication Date:
1992
detail.hit.zdb_id:
1477300-4
SSG:
12
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