Proper cytoskeleton α‐tubulin distribution is concomitant to tyrosine phosphorylation during in vitro capacitation and acrosomal reaction in human spermatozoa

Spermatozoa motility is a key parameter during the fertilization process. In this context, spermatozoa tyrosine protein phosphorylation and an appropriate cytoskeleton α‐tubulin distribution are some of the most important physiological events involved in motility. However, the relationship between these two biomarkers remains poorly defined. Here, we characterized simultaneously by immunocytochemistry the α‐tubulin (TUBA4A) distribution and the tyrosine phosphorylation at flagellum before capacitation, during different capacitation times (1 and 4 hr), and after acrosome reaction induction in human spermatozoa. We found that the absence of spermatozoa phosphorylation in tyrosine residues positively and significantly correlated (p < 0.05) with the terminal piece α‐tubulin flagellar distribution in all physiological conditions. Conversely, we observed a positive significant correlation (p < 0.01) between phosphorylated spermatozoa and continuous α‐tubulin distribution in spermatozoa flagellum, independently of the physiological condition. Similarly, the subpopulation of spermatozoa with tyrosine phosphorylated and continuous α‐tubulin increases with longer capacitation times and after the acrosome reaction induction. Overall, these findings provide novel insights into the post‐transcriptional physiological events associated to α‐tubulin and the tyrosine phosphorylation during fertilization, which present potential implications for the improvement of spermatozoa selection methods.This research was supported by Human Fertility Cathedra of the University of Alicante, VIOGROB-186, and the project of the Ministry of Economy and Competitiveness AGL2015-70159-P

Natural and modified promoters for tailored metabolic engineering of the yeast Saccharomyces cerevisiae

The ease of highly sophisticated genetic manipulations in the yeast Saccharomyces cerevisiae has initiated numerous initiatives towards development of metabolically engineered strains for novel applications beyond its traditional use in brewing, baking, and wine making. In fact, baker's yeast has become a key cell factory for the production of various bulk and fine chemicals. Successful metabolic engineering requires fine-tuned adjustments of metabolic fluxes and coordination of multiple pathways within the cell. This has mostly been achieved by controlling gene expression at the transcriptional level, i.e., by using promoters with appropriate strengths and regulatory properties. Here we present an overview of natural and modified promoters, which have been used in metabolic pathway engineering of S. cerevisiae. Recent developments in creating promoters with tailor-made properties are also discussed.</p