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Jonas Rutishauser

Publications and source records attributed to Jonas Rutishauser.

7 recordsLinked to original sources
PubMed2006

The role of statins in clinical medicine--LDL--cholesterol lowering and beyond.

In the past years, statins have emerged as the most important class of lipid lowering agents. Through inhibition of HMG-CoA reductase, they restrict the rate-limiting step of cholesterol synthesis, which leads to upregulation of LDL receptors on the cell membrane and thus reduction of atherogenic LDLs. This effect translates into clinical benefit by reducing cardiovascular events both in primary and secondary prevention settings. As an approximate rule, statin therapy leads to a relative risk reduction of 25-30% in most of the large randomised controlled trials. Stroke risk is reduced to a similar degree. Despite initial concerns, the currently available statins have a favourable safety profile; however, potential interactions with other drugs must be considered. Recently, characteristics unrelated to LDL lowering have been intensively studied. These pleiotropic statin effects result from decreased levels of isoprenoid intermediates of cholesterol synthesis. They include--among others--anti-inflammatory, anti-proliferative, and immunomodulatory actions. Pleiotropic effects favourably influence pathomechanisms of plaque formation. Furthermore, they may prove beneficial in the prevention or treatment of diseases unrelated to atherosclerosis, eg rheumatoid arthritis, multiple sclerosis, or cancer.

Cardiovascular Diseases↗
PubMed2004

Degradation of wild-type vasopressin precursor and pathogenic mutants by the proteasome.

Mutations in the gene encoding the antidiuretic hormone arginine vasopressin cause autosomal dominant neurogenic diabetes insipidus. Autoptic data in affected individuals suggest that the neurons expressing mutant vasopressin undergo selective degeneration. Expression studies have shown that the mutants are retained in the endoplasmic reticulum, but how this trafficking defect is linked to neurotoxicity is unknown. One possibility is that unsecreted mutant precursors, or degradation products thereof, are cytotoxic. We therefore investigated the fate of endoplasmic reticulum-retained pathogenic mutants. Our data show that the mutants are retrotranslocated to the cytosol and degraded by the proteasome. In the presence of proteasomal inhibitors, three distinct un- or deglycosylated cytosolic species of vasopressin precursors were stabilized: pre-pro-vasopressin, pro-vasopressin, and an N-terminally truncated form. In addition to the retrotranslocated forms, a fraction of the newly synthesized precursor was not translocated, but was synthesized into the cytosol due to inefficient function of the vasopressin signal peptide. As a result, cytosolic pre-pro-vasopressin and its degradation product were also recovered when wild-type vasopressin was expressed. Cytosolic forms of vasopressin might trigger cytotoxicity in vivo, as has been proposed in the case of prion protein, which also contains an inefficient N-terminal signal peptide.

Amino Acid Sequence↗
PubMed2004

Expression of regulated secretory proteins is sufficient to generate granule-like structures in constitutively secreting cells.

The formation of secretory granules and regulated secretion are generally assumed to occur only in specialized endocrine, neuronal, or exocrine cells. We discovered that regulated secretory proteins such as the hormone precursors pro-vasopressin, pro-oxytocin, and pro-opiomelanocortin, as well as the granins secretogranin II and chromogranin B but not the constitutive secretory protein alpha(1)-protease inhibitor, accumulate in granular structures at the Golgi and in the cell periphery in transfected COS-1 fibroblast cells. The accumulations were observed in 30-70% of the transfected cells expressing the pro-hormones and for virtually all of the cells expressing the granins. Similar structures were also generated in other cell lines believed to be lacking a regulated secretory pathway. The accumulations resembled secretory granules morphologically in immunofluorescence and electron microscopy. They were devoid of markers of the endoplasmic reticulum, endosomes, and lysosomes but in part stained positive for the trans-Golgi network marker TGN46, consistent with their formation at the trans-Golgi network. When different regulated proteins were coexpressed, they were frequently found in the same granules, whereas alpha(1)-protease inhibitor could not be detected in accumulations formed by secretogranin II, demonstrating segregation of regulated from constitutive secretory proteins. In pulse-chase experiments, significant intracellular storage of secretogranin II and chromogranin B was observed and secretion of retained secretogranin II was stimulated with the calcium ionophore A23187. The results suggest that expression of regulated cargo proteins is sufficient to generate structures that resemble secretory granules in the background of constitutively secreting cells, supporting earlier proposals on the mechanism of granule formation.

Animals↗
PubMed2004

Functional characterization of pendrin in a polarized cell system. Evidence for pendrin-mediated apical iodide efflux.

Pendred's syndrome is an autosomal recessive disorder characterized by sensorineural deafness, goiter, and impaired iodide organification. It is caused by mutations in the PDS/SLC26A4 gene that encodes pendrin. Functionally, pendrin is a transporter of chloride and iodide in Xenopus oocytes and heterologous mammalian cells and a chloride/base exchanger in beta-intercalated cells of the renal cortical collecting duct. The partially impaired thyroidal iodide organification in Pendred's syndrome suggests a possible role of pendrin in iodide transport at the apical membrane of thyroid follicular cells, but experimental evidence for this concept is lacking. The iodide transport properties of pendrin were determined in polarized Madin-Darby canine kidney cells expressing the sodium iodide symporter (NIS), pendrin, or NIS and pendrin using a bicameral system-permitting measurement of iodide content in the basal, intracellular, and apical compartments. Moreover, we determined the functional consequences of two naturally occurring mutations (L676Q and FS306>309X). In polarized Madin-Darby canine kidney cells, NIS mediates uptake at the basolateral membrane. Only minimal amounts of iodide reach the apical compartment in the absence of pendrin. In cells expressing NIS and pendrin, pendrin mediates transport of iodide into the apical chamber. Wild type pendrin also mediates iodide efflux in transiently transfected cells. In contrast, both pendrin mutants lose the ability to promote iodide efflux. These results provide evidence that pendrin mediates apical iodide efflux from polarized mammalian cells loaded with iodide. Consistent with the partial organification defect observed in patients with Pendred's syndrome, naturally occurring mutations of pendrin lead to impaired transport of iodide.

Adenoviridae↗
PubMed2002

Endoplasmic reticulum storage diseases.

The endoplasmic reticulum represents the cell's quality control site for accurate folding of secretory and membrane proteins. Quality control is achieved through the association of ER chaperones with unfolded or misfolded polypeptide chains. In the ER stress response, upregulation of chaperones occurs as a consequence of misfolded proteins accumulating in the ER lumen; if these proteins fail to assume their native structure, they are retained in the ER and targeted for degradation by the proteasome. ER storage diseases (ERSDs) are a group of genetically based disorders in which mutant proteins fail to pass the ER quality control. Because all eukaryotic cells contain the ER, the clinical phenotype of ERSDs is very heterogeneous. Disease may result from the mere lack of the mutant protein in question and/or may be caused indirectly by toxic effects of the misfolded protein or aggregates thereof on the cell. Additionally, the cell's reaction to the ER stress may include signaling pathways which are ultimately detrimental. Experimentally, ERSDs serve as models to study the cellular reactions to a variety of perturbations. In particular, understanding the links between ER stress and cell degeneration may give valuable insights into the pathogenesis of other diseases where the accumulation of indigestible toxic material leads to cell injury.

Endoplasmic Reticulum↗
PubMed2002

Clinical and molecular analysis of three families with autosomal dominant neurohypophyseal diabetes insipidus associated with a novel and recurrent mutations in the vasopressin-neurophysin II gene.

OBJECTIVE: To test further the hypothesis that autosomal dominant neurohypophyseal diabetes insipidus (adFNDI) is caused by heterozygous mutations in the vasopressin-neurophysin II (AVP-NPII) gene that exert a dominant negative effect by producing a precursor that misfolds, accumulates and eventually destroys the neurosecretory neurons. METHODS: Antidiuretic function, magnetic resonance imaging (MRI) of the posterior pituitary and AVP-NPII gene analysis were performed in 10 affected members of three unreported families with adFNDI. RESULTS: As in previously studied patients, adFNDI apparently manifested after birth, was due to a partial or severe deficiency of AVP, and was associated with absence or diminution of the hyperintense MRI signal normally emitted by the posterior pituitary, and with a heterozygous mutation in the AVP-NPII gene. In family A, a transition 275G-->A, which predicts replacement of cysteine 92 by tyrosine (C92Y), was found in the index patient, but not in either parent, indicating that it arose de novo. The six affected members of family B had a transversion 160G-->C, which predicts replacement of glycine 54 by arginine (G54R). It appeared de novo in the oldest affected member, and was transmitted in a dominant manner. In family C, six of 15 living affected members were tested and all had a novel transition, 313T-->C, which predicts replacement of cysteine 105 by arginine (C105R). It, too, was transmitted in a dominant manner. As in other patients with adFNDI, the amino acids replaced by the mutations in these three families are known to be particularly important for correct and efficient folding of the precursor. CONCLUSIONS: These findings are consistent with the malfolding/toxicity hypothesis underlying the pathogenesis of adFNDI. Moreover, they illustrate the value of genetic analysis in all patients who develop idiopathic diabetes insipidus in childhood, even if no other family members are affected.

Adult↗