Biology subjects

Pires, M. F.

Publications and source records attributed to Pires, M. F..

3 recordsLinked to original sources

bioRxiv2023

Dual stop codon suppression in mammalian cells with genomically integrated genetic code expansion machinery

Genetic code expansion via stop codon suppression is a powerful strategy to engineer proteins. Pyrrolysyine-tRNA (tRNAPyl)/pyrrolysyl-tRNA synthetase (PylRS) pairs from methanogenic archaea and engineered bacterial tRNA/aminoacyl-tRNA synthetases (aaRS) pairs are used for site-specific incorporation of noncanonical amino acids (ncAAs) in response to stop codons in mammalian cells. Routinely, ncAA incorporation is achieved by transient expression of the tRNA/aaRS pair leading to heterogeneous suppression. Genomic integration of tRNA/aaRS expression cassettes for more homogenous, adjustable and reproducible levels of protein, containing one or more ncAA, will greatly benefit protein engineering, chemical control and imaging applications in mammalian cells. Here, we demonstrate that piggyBac-mediated genomic integration of archaeal tRNAPyl/PylRS or bacterial tRNA/aaRS pairs, using a modular plasmid design with multi-copy tRNA arrays, allows for homogeneous and efficient, genetically encoded ncAA incorporation in diverse mammalian cell lines. We assess opportunities and limitations of using ncAAs for fluorescent labeling applications in stable cell lines. We explore simultaneous suppression of ochre and opal stop codons and finally incorporate two distinct ncAAs with mutually orthogonal click chemistries for site-specific, dual fluorophore labeling of a cell surface receptor on live mammalian cells.

cell biology↗

bioRxiv2022

Transcriptional lability of brain oxytocin receptor (Oxtr) generates diversity in brain OXTR distribution and social behaviors

Although oxytocin (OXT) exhibits a highly conserved neuroanatomical pattern among vertebrates, the distribution of OXT receptor (OXTR) in brain varies considerably across species and is associated with species-typical social behavior. To investigate the genomic basis of the phylogenetic plasticity in brain Oxtr expression and its social behavioral consequences, we generated transgenic mice carrying a bacteria artificial chromosome (BAC) harboring the entire prairie vole Oxtr locus and flanking intergenic regulatory regions. We established eight independent "volized" mouse lines expressing prairie vole Oxtr (pvOxtr). Strikingly, despite conserved Oxtr expression in mammary gland of all transgenic mouse lines, each line displayed a unique pattern of brain expression distinct from both mice and prairie voles. Together with topologically associating domain (TAD) structure analysis with mouse genome, our findings suggest that unlike Oxt, Oxtr expression patterns in brain, involve contributions of distal regulatory elements beyond the BAC insert. In contrast, Oxtr expression in peripheral tissues appears resistant to such distal influences. Moreover, the "volized" mouse lines with different brain Oxtr expression patterns showed differences in partner preference and maternal behaviors, providing direct functional evidence that variation in brain Oxtr expression can drive differences in social behaviors. We propose that brain Oxtr expression is transcriptionally sensitive to long-range interactions with distal genomic elements, rendering it more susceptible to diverse regulatory influences. This supports a model in which regulatory flexibility facilitates the evolutionary diversification of social behavior, while maintaining essential peripheral Oxtr expression.

neuroscience↗

bioRxiv2022

Immunomodulatory actions of a kynurenine-derived endogenous electrophile.

The inflammatory upregulation of kynurenine metabolism induces immunomodulatory responses via incompletely understood mechanisms. We report that increases in cellular and systemic kynurenine levels yield the electrophilic derivative kynurenine-carboxyketoalkene (Kyn-CKA), as evidenced by the accumulation of thiol-conjugates and saturated metabolites. Under physiological conditions, Kyn-CKA induces Nrf2-regulated genes and inhibits NF-{kappa}B and NLRP3-dependent pro-inflammatory signaling. Sickle Cell Disease (SCD) is a hereditary hemolytic condition characterized by basal inflammation and recurrent vaso-occlusive crises. Both a transgenic SCD murine model and SCD patients exhibit increased kynurenine synthesis and elevated Kyn-CKA metabolite levels. Plasma hemin and kynurenine concentrations are positively correlated, indicating that Kyn-CKA synthesis in SCD is upregulated during pathogenic vascular stress. Remarkably, exogenous administration of Kyn-CKA abrogated pulmonary microvasculature occlusion in SCD mice, an important factor in the development of lung injury. These findings demonstrate that the upregulation of kynurenine synthesis and its metabolism to Kyn-CKA is an adaptive response that attenuates inflammation and protects tissues. One-Sentence SummaryKyn-CKA is a kynurenine-derived signaling mediator that transduces its immunomodulatory protective actions and attenuates vaso-occlusion in sickle cell disease.

immunology↗