A yeast genetic assay for caspase cleavage of the amyloid-beta precursor protein

Type 3 Diabetes: Cross Talk between Differentially Regulated Proteins of Type 2 Diabetes Mellitus and Alzheimer's Disease

Type 3 Diabetes (T3D) is a neuroendocrine disorder that represents the progression of Type 2 Diabetes Mellitus (T2DM) to Alzheimer’s disease (AD). T3D contributes in the increase of the total load of Alzheimer’s patients worldwide. The protein network based strategies were used for the analysis of protein interactions and hypothesis was derived describing the possible routes of communications among proteins. The hypothesis provides the insight on the probable mechanism of the disease progression for T3D. The current study also suggests that insulin degrading enzyme (IDE) could be the major player which holds the capacity to shift T2DM to T3D by altering metabolic pathways like regulation of beta-cell development, negative regulation of PI3K/AKT pathways and amyloid beta degradation.

γ-Secretase inhibitors and modulators

γ-Secretase is a fascinating, multi-subunit, intramembrane cleaving protease that is now being considered as a therapeutic target for a number of diseases. Potent, orally bioavailable γ-secretase inhibitors (GSIs) have been developed and tested in humans with Alzheimer's disease (AD) and cancer. Preclinical studies also suggest the therapeutic potential for GSIs in other disease conditions. However, due to inherent mechanism based-toxicity of non-selective inhibition of γ-secretase, clinical development of GSIs will require empirical testing with careful evaluation of benefit versus risk. In addition to GSIs, compounds referred to as γ-secretase modulators (GSMs) remain in development as AD therapeutics. GSMs do not inhibit γ-secretase, but modulate γ-secretase processivity and thereby shift the profile of the secreted amyloid β peptides (Aβ) peptides produced. Although GSMs are thought to have an inherently safe mechanism of action, their effects on substrates other than the amyloid β protein precursor (APP) have not been extensively investigated. Herein, we will review the current state of development of GSIs and GSMs and explore pertinent biological and pharmacological questions pertaining to the use of these agents for select indications. This article is part of a Special Issue entitled: Intramembrane Proteases.

Contribution of yeast models to neurodegeneration research

As a model organism Saccharomyces cerevisiae has greatly contributed to our understanding of many fundamental aspects of cellular biology in higher eukaryotes. More recently, engineered yeast models developed to study endogenous or heterologous proteins that lay at the root of a given disease have become powerful tools for unraveling the molecular basis of complex human diseases like neurodegeneration. Additionally, with the possibility of performing target-directed large-scale screenings, yeast models have emerged as promising first-line approaches in the discovery process of novel therapeutic opportunities against these pathologies. In this paper, several yeast models that have contributed to the uncovering of the etiology and pathogenesis of several neurodegenerative diseases are described, including the most common forms of neurodegeneration worldwide, Alzheimer's, Parkinson's, and Huntington's diseases. Moreover, the potential input of these cell systems in the development of more effective therapies in neurodegeneration, through the identification of genetic and chemical suppressors, is also addressed.

Use of yeast as a model system to investigate protein conformational diseases

Protein conformational diseases arise when a cellular protein adopts an aberrant shape that either directly or indirectly alters the physiology of its host cell. Notable conformational diseases include cystic fibrosis, Huntington's disease, the prion-related diseases, Alzheimer's disease, and antitrypsin deficiency. In principle, the severity and progression of conformational diseases can be altered by cellular factors that recognize and attempt to ameliorate the harmful effects of the disease-causing, misshapen protein. To better define the mechanistic underpinnings of cellular factors that mediate quality control, and to understand why a single misfolded protein can impact cell viability, specific proteins that cause each of the diseases listed above have been expressed in a model eukaryote, the yeast Saccharomyces cerevisiae. In this review, we describe what has been learned from these studies, and speculate on future uses of yeast expression systems.

Saccharomyces cerevisiae is capable of de Novo pantothenic acid biosynthesis involving a novel pathway of beta-alanine production from spermine

Pantothenic acid and beta-alanine are metabolic intermediates in coenzyme A biosynthesis. Using a functional screen in the yeast Saccharomyces cerevisiae, a putative amine oxidase, encoded by FMS1, was found to be rate-limiting for beta-alanine and pantothenic acid biosynthesis. Overexpression of FMS1 caused excess pantothenic acid to be excreted into the medium, whereas deletion mutants required beta-alanine or pantothenic acid for growth. Furthermore, yeast genes ECM31 and YIL145c, which both have structural homology to genes of the bacterial pantothenic acid pathway, were also required for pantothenic acid biosynthesis. The homology of FMS1 to FAD-containing amine oxidases and its role in beta-alanine biosynthesis suggested that its substrates are polyamines. Indeed, we found that all the enzymes of the polyamine pathway in yeast are necessary for beta-alanine biosynthesis; spe1Delta, spe2Delta, spe3Delta, and spe4Delta are all beta-alanine auxotrophs. Thus, contrary to previous reports, yeast is naturally capable of pantothenic acid biosynthesis, and the beta-alanine is derived from methionine via a pathway involving spermine. These findings should facilitate the identification of further enzymes and biochemical pathways involved in polyamine degradation and pantothenic acid biosynthesis in S. cerevisiae and raise questions about these pathways in other organisms.