title: Hypoxia induces the synthesis of tropomyosin in cultured porcine pulmonary artery endothelial cells.
abstract: The present study examined the effect of hypoxia on protein synthesis by porcine pulmonary artery endothelial cells (PAEC). Hypoxia decreased protein synthesis in PAEC, but two-dimensional gel electrophoresis of [35S]methionine-labeled PAEC proteins demonstrated the increased synthesis of a set of proteins having molecular masses (M(r)) of 35, 36.5, 45, 116, and 205 kDa. The synthesis of the 35-, 36.5-, and 45-kDa proteins was increased in preconfluent and postconfluent cells. The 35- and 45-kDa proteins were not induced by hyperthermia, whereas the 36.5-kDa protein was induced slightly by hyperthermia. Induction of the 36.5- and 45-kDa proteins required a minimum of 8 h of hypoxia, whereas induction of the 35-kDa protein required only 4 h of exposure to hypoxia. The upregulated synthesis of the 35-, 36.5-, and 45-kDa proteins was reversible with return to normoxia. Actinomycin D, an inhibitor of transcription, did not block the hypoxic induction of the 35- and 36.5-kDa proteins but did block induction of the 45-kDa protein. The partial amino acid sequence of the 35-kDa protein obtained from cyanogen bromide cleavage of the molecule was Asp-Ala-Ile-Lys-Lys-Lys-Met-Gln-Met-Leu-Lys-Leu-Asp-Lys-Glu. This partial sequence of the 35-kDa protein identically matches the sequence of tropomyosin. Amino acid composition data and the isoelectric point (4.8) were also typical of tropomyosin. Finally, specific cross-reactivity was detected between the 35-kDa protein and a monoclonal antibody to chicken gizzard tropomyosin on immunoblot. Thus hypoxia induces the synthesis of tropomyosin, a major microfilament-associated protein, in porcine PAEC in monolayer culture.
authors.affiliation: Department of Medicine, University of Florida College of Medicine, Gainesville.
authors.forename: U J
authors.initials: UJ
authors.lastname: Rao
authors.forename: N D
authors.initials: ND
authors.lastname: Denslow
authors.forename: E R
authors.initials: ER
authors.lastname: Block
mesh_terms: D000595:Amino Acid Sequence; D000596:Amino Acids / Q000032:analysis; D000818:Animals; D002478:Cells, Cultured; D004730:Endothelium, Vascular / Q000166:cytology / Q000378:metabolism*; D000860:Hypoxia / Q000378:metabolism*; D008969:Molecular Sequence Data; D008970:Molecular Weight; D009124:Muscle Proteins / Q000096:biosynthesis; D011651:Pulmonary Artery / Q000166:cytology / Q000378:metabolism*; D013552:Swine; D014335:Tropomyosin / Q000096:biosynthesis* / Q000737:chemistry / Q000235:genetics
chemical_list: D000596:Amino Acids; D009124:Muscle Proteins; D014335:Tropomyosin