Hepatic Farnesoid X-Receptor Isoforms α2 and α4 Differentially Modulate Bile Salt and Lipoprotein Metabolism in Mice

The nuclear receptor FXR acts as an intracellular bile salt sensor that regulates synthesis and transport of bile salts within their enterohepatic circulation. In addition, FXR is involved in control of a variety of crucial metabolic pathways. Four FXR splice variants are known, i.e. FXRα1-4. Although these isoforms show differences in spatial and temporal expression patterns as well as in transcriptional activity, the physiological relevance hereof has remained elusive. We have evaluated specific roles of hepatic FXRα2 and FXRα4 by stably expressing these isoforms using liver-specific self-complementary adeno-associated viral vectors in total body FXR knock-out mice. The hepatic gene expression profile of the FXR knock-out mice was largely normalized by both isoforms. Yet, differential effects were also apparent; FXRα2 was more effective in reducing elevated HDL levels and transrepressed hepatic expression of Cyp8b1, the regulator of cholate synthesis. The latter coincided with a switch in hydrophobicity of the bile salt pool. Furthermore, FXRα2-transduction caused an increased neutral sterol excretion compared to FXRα4 without affecting intestinal cholesterol absorption. Our data show, for the first time, that hepatic FXRα2 and FXRα4 differentially modulate bile salt and lipoprotein metabolism in mice

Antimicrobial effects of fruit and flower anthocyanins

• Our research suggest that anthocyanins are promising anti-bacterial agents • The antimicrobial effects are highly dependent on the source of the anthocyanin-extract • Rose-anthocyanins appear to posses the strongest anti-bacterial effects • Gram-positive strains appear to be more sensitive compared to gram-negative strains • Future research efforts should focus on different anthocyanin entitie

The human HSP70/HSP40 chaperone family : a study on its capacity to combat proteotoxic stress

All cells are constantly threatened by both physical and chemical stress factors that can damage e.g. the DNA and proteins. Whereas the molecular mechanisms responsible for DNA repair have been studied in great detail, the mechanism underlying the repair and disposal of damaged proteins are far less investigated and less understood. It is well known that DNA damage in combination with a malfunctioning repair mechanism may ultimately lead to diseases such as cancer. But also damaged proteins and impaired protein repair are implicated in disease, in particular neurodegenerative diseases such as Huntingtons disease, various types of Spinocerebellar ataxias, Parkinsons disease and Alzheimers disease. All these diseases share a relative late age of onset and are currently incurable. To combat protein damage, cells contain large families of proteins, named chaperones, which assist in protein folding and repair. So far, only a minority of these proteins have been studied and the largest chaperone family in humans consists of the HSP70/HSP40 family. In this thesis, the results of the first elaborate and detailed study on the human HSP70/HSP40 family is presented. The characteristics of the family are systematically analyzed and compared using both bioinformatics as well as cell biological approaches. The functional chaperone activity is measured in various cellular models for neurodegenerative diseases. Our results show that a number of HSP40 chaperone proteins show a highly promising activity to suppress various progressive characteristics typical for neurodegenerative diseases.

Single-step gene knockout of the SUC2 gene in saccharomyces cerevisiae:a laboratory exercise for undergraduate students

This article describes a laboratory experiment about generating a knock-out in bakers yeast. Moreover, it describes how to embed this experiment in an Bachelors educational program

The diverse members of the mammalian HSP70 machine show distinct chaperone-like activities

International audienceHumans contain many HSP70/HSPA and HSP40/DNAJ encoding genes, most of which are localized in the cytosol. To test for possible functional differences or/and substrate specificity, we assessed the effect of overexpression of each of these HSPs on refolding of heat-denatured luciferase and on the suppression of aggregation of a non-foldable polyglutamine (poly-Q) expanded Huntingtin fragment. Overexpressed chaperones that suppressed poly-Q aggregation were found not to be able to stimulate luciferase refolding. Inversely, chaperones that supported luciferase refolding were poor suppressors of polyQ aggregation. This was not related to client specificity per se, as the poly-Q aggregation inhibitors often also suppressed heat-induced aggregation of luciferase. Surprisingly, the exclusively heat-inducible HSPA6 lacks both luciferase refolding and poly-Q aggregation-suppressing activities. Furthermore, whereas overexpression of HSPA1A protected cells from heat-induced cell death, overexpression of HSPA6 did not. Inversely, siRNA mediated blocking of HSPA6 did not impair the development of heat-induced thermotolerance. Yet, HSPA6 has a functional substrate-binding domain and possesses intrinsic ATPase activity that is as high as that of the canonical HSPA1A when stimulated by J-proteins. In vitro data suggest that this may be relevant to substrate specificity as purified HSPA6 could not chaperone heat-unfolded luciferase but was able to assist in reactivation of heat-unfolded p53. So, even within the highly sequence-conserved HSPA family, functional differentiation is larger than expected with HSPA6 being an extreme example that may have evolved to maintain specific critical functions under conditions of severe stress