The consequence of nucleotide substitutions in the triosephosphate isomerase (TPI) gene promoter

Heterologous (Over) Expression of Human SoLute Carrier (SLC) in Yeast: A Well-Recognized Tool for Human Transporter Function/Structure Studies

For more than 20 years, yeast has been a widely used system for the expression of human membrane transporters. Among them, more than 400 are members of the largest transporter family, the SLC superfamily. SLCs play critical roles in maintaining cellular homeostasis by transporting nutrients, ions, and waste products. Based on their involvement in drug absorption and in several human diseases, they are considered emerging therapeutic targets. Despite their critical role in human health, a large part of SLCs' is 'orphans' for substrate specificity or function. Moreover, very few data are available concerning their 3D structure. On the basis of the human health benefits of filling these knowledge gaps, an understanding of protein expression in systems that allow functional production of these proteins is essential. Among the 500 known yeast species, S. cerevisiae and P. pastoris represent those most employed for this purpose. This review aims to provide a comprehensive state-of-the-art on the attempts of human SLC expression performed by exploiting yeast. The collected data will hopefully be useful for guiding new attempts in SLCs expression with the aim to reveal new fundamental data that could lead to potential effects on human health.

Triosephosphate isomerase gene promoter variation: -5G/A and -8G/A polymorphisms in clinical malaria groups in two African populations

TPI1 promoter polymorphisms occur in high prevalence in individuals from African origin. Malaria-patients from Angola and Mozambique were screened for the TPI1 gene promoter variants rs1800200A>G, (-5G>A), rs1800201G>A, (-8G>A), rs1800202T>G, (-24T>G), and for the intron 5 polymorphism rs2071069G>A, (2262G>A). -5G>A and -8G>A variants occur in 47% and 53% in Angola and Mozambique, respectively while -24T>G was monomorphic for the wild-type T allele. Six haplotypes were identified and -8A occurred in 45% of the individuals, especially associated with the GAG haplotype and more frequent in non-severe malaria groups, although not significantly. The arising and dispersion of -5G>A and -8G>A polymorphisms is controversial. Their age was estimated by analyses of two microsatellite loci, CD4 and ATN1, adjacent to TPI1 gene. The -5G>A is older than -8G>A, with an average estimate of approximately 35,000 years. The -8A variant arose in two different backgrounds, suggesting independent mutational events. The first, on the -5G background, may have occurred in East Africa around 20,800 years ago; the second, on the -5A background, may have occurred in West Africa some 7500 years ago. These estimates are within the period of spread of agriculture and the malaria mosquito vector in Africa, which could has been a possible reason for the selection of -8A polymorphism in malaria endemic countries.

Analysis of TPI gene promoter variation in three sub-Saharan Africa population samples

Population samples from Angola, Mozambique, and S. Tomé e Príncipe were screened for the TPI gene promoter variants -5A-->G, -8G-->A and -24T-->G. Three haplotypes were identified in the three populations: the haplotype -5A-8G-24T (average frequency 65.3%) and two less common haplotypes -5G-8G-24T (average frequency 24.7%) and -5G-8A-24T (average frequency 10.0%). A population sample from Central Portugal showed the haplotype -5A-8G-24T in 139 chromosomes and one subject heterozygous for haplotype -5G-8A-24G. The exact test of sample differentiation among three groups of malaria-infected individuals classified according to the severity of the disease showed no significant differences. We confirmed TPI gene diversity in sub-Saharan Africa, but we could not detect any association between TPI promoter variation and a malarial protective effect. Larger scale epidemiological studies are thus required to clarify this putative mechanism of natural host defense against this worldwide public health problem.

Triosephosphate isomerase deficiency: historical perspectives and molecular aspects

In this chapter, the original descriptions and pre-molecular studies of triosephosphate isomerase (TPI) deficiency are summarized, and the molecular aspects of the disease presented. The gene is well characterized, and several mutations have been described. Structure-function studies have led to an increased understanding of impaired catalysis. All kindreds that have been studied with the predominant Glu104Asp mutation are linked by a common haplotype, indicating descent from a common ancestor. Variant upstream substitutions occur in high frequency in persons of African and East Asian lineage and in lower frequency in other groups, but the possible role, if any, of these variants in clinical TPI deficiency requires further investigation. The possible contribution of deviant lipid metabolism to the pathogenesis of the disorder has been extensively investigated, and an intriguing new area of inquiry is the apparent cell-to-cell transfer of enzyme in cell culture systems, raising the question of the feasibility of enzyme or gene replacement therapy.