Biomedical subjects

Y Aratani

Publications and source records attributed to Y Aratani.

32 records · Page 2Linked to original sources

PubMed1990

Production of two variant laminin forms by endothelial cells and shift of their relative levels by angiostatic steroids.

Organization of endothelium as the lining of the cardiovascular system is supported by basement membrane. The important role of laminin and other basement membrane proteins is assumed in the angiogenesis. We show here that cultured endothelial cells produce two forms of laminin, and their relative levels are changed by antiangiogenic steroids. The synthesis of laminin subunits by endothelial cells isolated from bovine aorta and from bovine pulmonary artery was studied by metabolic labeling with [35S]methionine. Both endothelial cells produced a novel laminin-related polypeptide (A' subunit) in addition to the A, B1, and B2 subunits. Two-dimensional sodium dodecyl sulfate gel electrophoretic analysis showed that the B1B2 complex was first formed and the A subunit joined it to form the AB1B2 complex or the A' subunit joined it to form A'B1B2 complex. This mechanism implied that replacement of subunits in the complex by a corresponding variant produces variety in the structure and function of laminin. The A'B1B2 complex was the major product in endothelial cells under normal culture conditions. An angiostatic steroid, medroxyprogesterone, suppressed the A' synthesis and stimulated the A synthesis. Consequently, the major product of bovine aorta endothelial cells was converted to AB1B2. Two types of intracellular precursors were identified for each laminin-related polypeptide. Since the precursors in a given complex were synchronized with regard to maturation, the assembly of AB1B2 and A'B1B2 complexes was suggested to occur at an early step of intracellular processing.

Animals↗

PubMed1990

Ascorbic acid phosphate stimulates type IV collagen synthesis and accelerates adipose conversion of 3T3-L1 cells.

We showed that the synthesis and secretion of type IV collagen, entactin, and laminin were enhanced when adipose conversion of 3T3-L1 cells at confluence was stimulated by hormones (Y. Aratani and Y. Kitagawa (1988) J. Biol. Chem. 263, 16163-16169). Ascorbic acid phosphate (Asc-P) stimulated the synthesis and secretion of type IV collagen and other collagens from both 3T3-L1 preadipocytes and adipocytes. The synthesis and secretion of laminin and entactin were not affected by Asc-P. The continuous addition of Asc-P stimulated cell growth and increased cell density at confluence 1.3-fold. Concomitantly, Asc-P remarkably accelerated the emergence of lipoprotein lipase, glycerophosphate dehydrogenase, and Oil Red O-stainable lipid droplets. These findings suggest an important role for type IV collagen in adipocyte differentiation.

Adipose Tissue↗

PubMed1988

Enhanced synthesis and secretion of type IV collagen and entactin during adipose conversion of 3T3-L1 cells and production of unorthodox laminin complex.

Synthesis and secretion of basement membrane proteins by 3T3-L1 adipocytes were studied by metabolic labeling of the cells with [35S]methionine. Enhanced synthesis and secretion of many polypeptides of high molecular weight were observed by stimulating the adipose conversion of 3T3-L1 fibroblasts with dexamethasone, 1-methyl-3-isobutylxanthine, and insulin. Among these polypeptides, alpha 1(IV) and alpha 2(IV) chains of collagen were identified based on specific immunoprecipitation and digestion with bacterial collagenase. Synthesis and secretion of alpha 1(IV) and alpha 2(IV) chains were negligible in the fibroblasts, but remarkably enhanced in adipocytes. Based on specific immunoprecipitation of a sulfated polypeptide of 150 kDa, enhanced (6-fold) synthesis and secretion of entactin were also demonstrated. Immunoprecipitation with anti-laminin antiserum showed synthesis of three polypeptides with sizes corresponding to B subunits but failed to demonstrate synthesis of the A subunit. Synthesis of these laminin-related polypeptides remained constant during the conversion. Nonreducing sodium dodecyl sulfate electrophoresis showed intracellular assembly of three laminin-related polypeptides into binary and ternary complexes in a similar sequence of AB1B2 formation via B1B2 in embryonal carcinoma F9 (Morita, A., Sugimoto, E., and Kitagawa, Y. (1985) Biochem. J. 229, 259-264). The ternary complex of laminin in 3T3-L1 cells had a size significantly smaller than AB1B2 complex in F9 cells. In this complex, a novel subunit appears to take the place of the A subunit. Thus, a novel laminin complex is produced by 3T3-L1 cells.

1-Methyl-3-isobutylxanthine↗

PubMed1988

Tyrosine sulfation is not the last modification of entactin before its secretion from 3T3-L1 adipocytes.

Tyrosine sulfation of entactin was studied by labeling of 3T3-L1 adipocytes with [35S]methionine or H2 35SO4 in the presence or absence of tunicamycin or monensin. Four precursors (EN1-4) at different steps of modification were detected in addition to mature entactin. Under normal conditions, EN2 and mature entactin were intracellular species, and the latter was sulfated and secreted. Inhibition of co-translational transfer of N-linked oligosaccharides by tunicamycin produced EN1 and EN3 as intracellular species, and EN3 was sulfated and secreted. Interruption of protein transport from medial to trans (distal) Golgi cisternae by monensin, and consequent blockage of terminal glycosylation caused intracellular accumulation of EN4. EN4 was sulfated and of different size compared to mature entactin. These facts suggested that tyrosine sulfation of entactin occurs in medial Golgi cisternae and is not the last modification before its secretion. Our results appeared inconsistent with recent observations by Baeuerle and Huttner [(1987) J. Cell Biol. 105, 2655-2664] that tyrosine sulfation of IgM occurred within the trans (distal) Golgi cisternae as the last modification before its exit from the Golgi complex.

Adipose Tissue↗

PubMed1987

Lithium ion reversibly inhibits inducer-stimulated adipose conversion of 3T3-L1 cells.

Adipose conversion of 3T3-L1 cells by inducers (dexamethasone, 1-methyl-3-isobutylxanthine and insulin) was inhibited by LiCl at concentrations from 2 to 20 mM. The effect of LiCl was reversible and the inhibited cells were converted to adipocytes when stimulated after the removal of LiCl. Inhibition by LiCl of adipose conversion was accompanied with a blockage of the enhanced [3H]thymidine incorporation and cellular proliferation that occurred before the adipocyte phenotype was expressed. Of the cations tested, only Li+ had these effects.

1-Methyl-3-isobutylxanthine↗

PubMed1986

Organization and transcription of the gluconate operon, gnt, of Bacillus subtilis.

The gluconate (gnt) operon of Bacillus subtilis has been cloned and sequenced. Analysis of the sequence (5482 base pairs) revealed four open reading frames, each of which was preceded by a Shine-Dalgarno sequence. These four frames were designated from the 5'-end as gntR, gntK, gntP, and gntZ. The gntR and gntK genes overlapped by 5 bases. The gntK and gntP gene products (consisting of 513 and 448 amino acids) were identified as gluconate kinase and permease, respectively, by means of insertional inactivation and deletion analysis of these genes subcloned in plasmid pC194. The functions of the gntR and gntZ gene products (243 and 468 amino acids) are presently unknown. S1 nuclease mapping and subcloning in a promoter probe vector (pPL603B) provided evidence that the gnt operon was transcribed as a polycistronic mRNA. Besides the gnt promoter about 40 base pairs upstream of the gntR gene, we detected two overlapping internal promoters between the gntP and gntZ genes. The gnt transcripts terminate about 45 base pairs downstream of the gntZ gene.

Amino Acid Sequence↗

PubMed1984

Catecholamine-stimulated protein phosphorylation in 3T3-L1 preadipocytes and adipocytes.

The endogenous protein phosphorylation stimulated by catecholamines was compared in 3T3-L1 preadipocytes and adipocytes. Phosphorylation of a protein with an approximate molecular weight of 57,000 was stimulated both in preadipocytes and adipocytes of 3T3-L1. Stimulated phosphorylation of four other proteins with approximate molecular weights of 90,000, 62,000, 48,000, and 32,000 was observed only in 3T3-L1 adipocytes. All of these proteins appeared to be localized in the microsomal fraction. Phosphorylation of these proteins was stimulated by norepinephrine, epinephrine, isoproterenol, dibutyryl cyclic AMP, theophylline, or 1-methyl-3-isobutylxanthine, but not by A23187. Among the phosphorylated proteins in 3T3-L1 adipocytes, the 62,000 dalton protein was most evident. Using this protein as a marker, it appeared that epinephrine and norepinephrine were effective in stimulating the phosphorylation at the same concentration range. This result was in clear contrast to the different affinities of these catecholamines for beta-receptors of 3T3-L1 adipocytes reported by Lai, Rosen, and Rubin (J. Biol. Chem. (1982) 257, 6691-6696). The phosphorylation of the 62,000 dalton protein in 3T3-L1 adipocytes was observed 1 min after the addition of norepinephrine, and dephosphorylation was observed within 10 min after the addition of propranolol.

Adipose Tissue↗

PubMed1981