Biomedical subjects

Stephane Richard

Publications and source records attributed to Stephane Richard.

5 recordsLinked to original sources

PubMed2006

Cloning and initial characterization of a new subunit for mammalian serine-palmitoyltransferase.

Serine-palmitoyltransferase (SPT) catalyzes the rate-limiting step of the de novo synthesis of sphingolipids. SPT is considered to be a heterodimer composed of two subunits, SPTLC1 and SPTLC2. Here we report the identification of a novel, third, SPT subunit (SPTLC3) that shows 68% homology to the SPTLC2 subunit. Quantitative real-time PCR revealed that SPTLC3 expression is highly variable between different human tissues and cell lines. The highest expression was observed in placenta tissue and human trophoblast cell lines. The overexpression of SPTLC3 in Hek293 cells, which otherwise have very little endogenous SPTLC3, led to a 2- to 3-fold increase in cellular SPT activity. Silencing of SPTLC3 expression in HepG2 cells or human trophoblast cells by transfecting SPTLC3-specific siRNA resulted in a significant reduction of cellular SPT activity. The expression of two SPT isoforms could be a cellular mechanism to adjust SPT activity to tissue-specific requirements of sphingolipid synthesis.

Acyltransferases↗

PubMed2003

Kep1 interacts genetically with dredd/caspase-8, and kep1 mutants alter the balance of dredd isoforms.

The Drosophila kep1 gene encodes an RNA binding protein related to the murine QUAKING apoptotic inducer. We have previously shown that kep1 can induce apoptosis when transfected into different cell lines. To better define the role of Kep1 in apoptosis, we generated kep1 null flies. These flies were viable, but females displayed reduced fertility, with approximately half of the eggs laid from kep1- homozygotes failing to hatch. In addition, loss of kep1 suppressed GMR-rpr-mediated apoptosis in the Drosophila eye, and kep1 mutant flies had increased susceptibility to Escherichia coli infection. We found that Kep1 bound dredd RNA in vitro, and that extracts prepared from kep1 mutant ovaries had markedly reduced proteolytic cleavage activity toward the caspase-8 target substrate IETD-7-amino-4-trifluoromethyl coumarin. We observed increased levels of the beta isoform of dredd mRNA in kep1 mutants as compared with wild-type. Taken together, our results suggest that Kep1 regulates apoptosis by influencing the processing of dredd RNA.

Animals↗

PubMed2003

Nephron sparing surgery for renal cell carcinoma and von Hippel-Lindau's disease: a single center experience.

PURPOSE: We reviewed the efficacy and safety of nephron sparing surgery for renal cell carcinoma in patients with von Hippel-Lindau disease. MATERIALS AND METHODS: Data were collated for all 56 patients with a mean age of 37.2 +/- 11.3 years (range 14 to 62) with von Hippel-Lindau disease who underwent radical nephrectomy or nephron sparing surgery at our department for 1 or more 25 to 60 mm renal cell carcinomas between 1988 and 2001. RESULTS: Overall 30 nephrectomies (33%) and 62 enucleations (67%) were performed for 62 bilateral and 30 unilateral tumors. For nephron sparing surgery estimated intraoperative blood loss was 175 +/- 231.7 cc (range 50 to 1,300), 97% of surgeries had vascular pedicle clamping for 32 +/- 10.4 minutes (range 10 to 50) and there were 4 immediate complications (1 perinephric abscess, 2 urinary fistulas and 1 acute renal failure requiring temporary dialysis). Renal atrophy was noted in 7.3% of cases. Tumor diameter was 31.2 +/- 10.7 mm (range 15 to 60) and recurrence diameter was 22 +/- 7.8 mm (range 4 to 45). Hospital stay was 7.6 +/- 2.4 days (range 5 to 21). Preoperative and postoperative creatinine was 1.0 +/- 0.2 (range 0.6 to 1.7) and 1.2 +/- 0.9 mg/dl (range 0.7 to 6.5), respectively. Median followup was 55.9 months. There were 17 local recurrences (27.4%) and no metastases at recurrence. The overall survival rate was 100% at 5 years and 67% at 10 years. CONCLUSIONS: Nephron sparing surgery is effective and, when feasible, it need not be called into question. However, it may probably be superseded by less invasive techniques for tumors less than 20 mm diagnosed early after these techniques have been validated in long-term trials.

Adolescent↗

PubMed2002

Symmetrical dimethylarginine methylation is required for the localization of SMN in Cajal bodies and pre-mRNA splicing.

The nuclear structures that contain symmetrical dimethylated arginine (sDMA)-modified proteins and the role of this posttranslational modification is unknown. Here we report that the Cajal body is a major epitope in HeLa cells for an sDMA-specific antibody and that coilin is an sDMA-containing protein as analyzed by using the sDMA-specific antibody and matrix-assisted laser desorption ionization time of flight mass spectrometry. The methylation inhibitor 5'-deoxy-5'-methylthioadenosine reduces the levels of coilin methylation and causes the appearance of SMN-positive gems. In cells devoid of Cajal bodies, such as primary fibroblasts, sDMA-containing proteins concentrated in speckles. Cells from a patient with spinal muscular atrophy, containing low levels of the methyl-binding protein SMN, localized sDMA-containing proteins in the nucleoplasm as a discrete granular pattern. Splicing reactions are efficiently inhibited by using the sDMA-specific antibody or by using hypomethylated nuclear extracts, showing that active spliceosomes contain sDMA polypeptides and suggesting that arginine methylation is important for efficient pre-mRNA splicing. Our findings support a model in which arginine methylation is important for the localization of coilin and SMN in Cajal bodies.

Antibodies↗

PubMed2002

A protein-domain microarray identifies novel protein-protein interactions.

Protein domains mediate protein-protein interactions through binding to short peptide motifs in their corresponding ligands. These peptide recognition modules are critical for the assembly of multiprotein complexes. We have arrayed glutathione S-transferase (GST) fusion proteins, with a focus on protein interaction domains, on to nitrocellulose-coated glass slides to generate a protein-domain chip. Arrayed protein-interacting modules included WW (a domain with two conserved tryptophans), SH3 (Src homology 3), SH2, 14.3.3, FHA (forkhead-associated), PDZ (a domain originally identified in PSD-95, DLG and ZO-1 proteins), PH (pleckstrin homology) and FF (a domain with two conserved phenylalanines) domains. Here we demonstrate, using peptides, that the arrayed domains retain their binding integrity. Furthermore, we show that the protein-domain chip can 'fish' proteins out of a total cell lysate; these domain-bound proteins can then be detected on the chip with a specific antibody, thus producing an interaction map for a cellular protein of interest. Using this approach we have confirmed the domain-binding profile of the signalling molecule Sam68 (Src-associated during mitosis 68), and have identified a new binding profile for the core small nuclear ribonucleoprotein SmB'. This protein-domain chip not only identifies potential binding partners for proteins, but also promises to recognize qualitative differences in protein ligands (caused by post-translational modification), thus getting at the heart of signal transduction pathways.

Amino Acid Sequence↗