Biomedical subjects

J K Burmester

Publications and source records attributed to J K Burmester.

26 records · Page 2Linked to original sources

PubMed1993

Phosphorylation is involved in transcriptional activation by the 1,25-dihydroxyvitamin D3 receptor.

The 1,25-dihydroxyvitamin D3 receptor becomes phosphorylated upon treatment with 1,25-dihydroxyvitamin D3. We have investigated the role of phosphorylation in the transcriptional activity induced by 1,25-dihydroxyvitamin D3 through its receptor. An active 1,25-dihydroxyvitamin D3-dependent transcription system was reconstituted in CV-1 cells by co-transfection of plasmids containing the rat 1,25-(OH)2D3 receptor DNA and a functional vitamin D response element (DRE) in a reporter gene construct. Treatment of these transiently transfected CV-1 cells with modulators of protein kinase A (8-Br-cAMP, PKIA and H-9) and phosphatases (Okadaic acid) resulted in mimicking or abolishing the transcriptional activity of 1,25-dihydroxyvitamin D3 in a receptor-dependent fashion. These modulators directly altered 1,25-dihydroxyvitamin D3 receptor phosphorylation. Therefore, the present results strongly suggest that phosphorylation plays a central role in the transcriptional activity of the 1,25-dihydroxyvitamin D3 receptor.

8-Bromo Cyclic Adenosine Monophosphate↗

PubMed1992

Identification of a structural domain that distinguishes the actions of the type 1 and 2 isoforms of transforming growth factor beta on endothelial cells.

A chimeric transforming growth factor beta (TGF-beta) molecule has been synthesized to map the amino acids responsible for the substantially greater activity of TGF-beta 1 than TGF-beta 2 on growth and migration of endothelial cells. This chimera consists of a dimer of a monomeric unit composed of amino acids 1-39 of TGF-beta 2, 40-82 of TGF-beta 1, and 83-112 of TGF-beta 2. Structural identity of the purified recombinant protein has been confirmed by immunoblotting and NH2-terminal sequencing. The biological potency of the TGF-beta 2-1-2 chimera was equal to that of TGF-beta 1 in inhibition of growth of both fetal bovine heart endothelial cells and rat epididymal fat pad microvascular endothelial cells. Similarly, the TGF-beta 2-1-2 chimera was nearly equivalent to TGF-beta 1 and at least 10-fold more active than TGF-beta 2 in inhibiting migration of bovine aortic endothelial cells. These results identify the sequence between amino acids 40-82 as an important region within TGF-beta that functions to specify a TGF-beta 1- or TGF-beta 2-like activity.

Animals↗

PubMed1992

Inhibition of growth by transforming growth factor-beta following fusion of two nonresponsive human carcinoma cell lines. Implication of the type II receptor in growth inhibitory responses.

Loss of growth regulation by transforming growth factor-beta (TGF-beta) may be an important step in carcinogenesis. We have used a cell fusion system to show that inhibition of growth by TGF-beta can be restored to carcinoma cell lines that are unresponsive to the inhibitory effects of TGF-beta. In a previous study, the EJ bladder carcinoma line was fused to the SW480 colon adenocarcinoma line and found to produce nontumorigenic hybrid cells along with one hybrid cell clone of low tumorigenicity. Here we show that the capacity of the nontumorigenic hybrid cells to respond to either TGF-beta 1 or TGF-beta 2 has been restored, while the parental or tumorigenic hybrid cells show little or no inhibition of growth following TGF-beta treatment. Cross-linking analyses with labeled TGF-beta 1 demonstrated much higher levels of the type II (85 kDa) receptor in the hybrid cells compared with the parental tumor lines. Both the parental and tumorigenic hybrid cell lines were capable of responding to TGF-beta as evidenced by increased levels of mRNA for fibronectin, type IV collagenase, and plasminogen activator inhibitor after treatment with TGF-beta 1. These results suggest that the type II receptor is necessary for mediating the effects of TGF-beta on inhibition of growth but not on gene activation of the hybrid cells.

Blotting, Northern↗

PubMed1992

Role of transforming growth factor-beta in maintenance of function of cultured neonatal cardiac myocytes. Autocrine action and reversal of damaging effects of interleukin-1.

The three isoforms of transforming growth factor-beta (TGF-beta) have previously been implicated in embryonic development of the heart as well as in repair of myocardial damage after ischemia/reperfusion injury. TGF-beta 1 has also been localized intracellularly to both mitochondria and contractile filaments of cardiac myocytes, although its role in these structures has not been defined. We now report that exogenous TGF-beta stabilizes the beating rate of neonatal rat cardiac myocytes cultured on fibroblast matrix, and sustains their spontaneous rhythmic beating in serum-free medium. Moreover, using blocking antibodies to TGF-beta, we show that endogenous TGF-beta secreted by these myocytes acts in an autocrine fashion to maintain their beating rate. In contrast, IL-1 beta, an inflammatory mediator secreted by immune cells during myocardial injury, inhibits the beating of cardiac myocytes, and TGF-beta can overcome this inhibition. The antagonistic effects of TGF-beta and IL-1 were not observed when the myocytes were cultured on gelatin, as compared to native fibroblast matrix. The data indicate that TGF-beta is an important regulator of contractile function of the heart and have significant implications for understanding cardiac physiology in health and disease.

Animals↗

PubMed1991

Localization of transforming growth factor-beta 1 in mitochondria of murine heart and liver.

Using both electron microscopic immunohistochemistry and cell fractionation techniques, we show that transforming growth factor-beta 1 (TGF-beta 1) is found in mitochondria of rat and mouse cardiac myocytes and rat hepatocytes. Four different polyclonal antibodies, raised against various epitopes encompassing the mature portion of the TGF-beta 1 molecule as well as the pro-region of its precursor, were used for the electron microscopy studies. The localization of TGF-beta 1 in mitochondria was confirmed by detection of the native peptide in mitochondria isolated from rat heart and liver; the majority of native TGF-beta 1 found in liver homogenates was recovered in highly pure mitochondrial fractions. The functional role of TGF-beta in the mitochondrion is unknown at present.

Animals↗

PubMed1988

Structure and regulation of the rat 1,25-dihydroxyvitamin D3 receptor.

Complementary DNA clones encoding the entire rat 1,25-dihydroxyvitamin D3 receptor were isolated, and the total 423-amino acid sequence was deduced. The amino acid sequence of the rat receptor is similar but not identical to the reported human receptor sequence. The cysteine-rich DNA-binding domain is completely conserved and the steroid-binding domain is greater than 93% conserved between rat and human. The cDNA was used as a probe in blot analysis of polyadenylylated RNA to show that the 1,25-dihydroxyvitamin D3 receptor mRNA is a single 4.4-kilobase mRNA that is expressed in intestine and kidney, slightly expressed in heart, and not detectable in liver and spleen. The receptor mRNA concentration is markedly increased during development of the rat intestine between day 14 and day 21, in accord with previous results obtained by measurement of receptor concentration by ligand binding or immunoblotting.

Amino Acid Sequence↗

PubMed1988

Isolation and expression of rat 1,25-dihydroxyvitamin D3 receptor cDNA.

The cDNA for the 1,25-dihydroxyvitamin D3 receptor has been isolated by screening a rat kidney lambda gt11 expression library with a mixture of three previously identified anti-receptor monoclonal antibodies. Protein produced from this cDNA reacts with each of the three monoclonal antibodies but does not react with an antibody specific for the porcine receptor or an irrelevant antibody. In addition, the expressed protein specifically binds 1,25-dihydroxyvitamin D3 but does not bind estradiol, progesterone, testosterone, cortisol, or aldosterone. The nucleotide sequence for this cDNA has been determined and used to deduce the amino acid sequence of the protein. This amino acid sequence contains a region that matches perfectly the partial amino acid sequence determined for the receptor isolated from porcine intestine. This amino acid sequence also closely matches the reported amino acid sequence of the putative DNA-binding finger of the avian 1,25-dihydroxyvitamin D3 receptor.

Amino Acid Sequence↗

PubMedDate not supplied

The cystic fibrosis conductance regulator gene exon sequence is normal in a patient with edematous eosinophilic nasal polyps.

Nasal polyps are the most common mass lesions found in the nose and their etiology is unknown. Nasal polyps from cystic fibrosis (CF) patients are histologically distinct from nasal polyps from patients without CF. It has been suggested that a mutation (G551D) of the cystic fibrosis transmembrane conductance regulator (CFTR) gene may play a role in nasal polyp formation in patients without CF. To investigate the possibility that this or other CFTR gene exon mutations are required for nasal polyp formation, the CFTR gene exons were sequenced from peripheral blood DNA derived from an adult patient with edematous eosinophilic nasal polyps and no personal or family history of CF. No mutations or deletions were identified in any of the CFTR exons. A single polymorphism (A or G) was found in exon 10, base pair 1540, amino acid 470. This polymorphism was detected in 11 of 16 subjects (69%) with edematous eosinophilic nasal polyps and 10 of 21 normal subjects (48%) without nasal polyps and was not statistically significant (p = 0.316). These results demonstrate that mutations of the CFTR coding region are not a prerequisite for the formation of edematous eosinophilic nasal polyps.

Cystic Fibrosis Transmembrane Conductance Regulato↗