Biology subjects

Lafita-Navarro, M. C.

Publications and source records attributed to Lafita-Navarro, M. C..

3 recordsLinked to original sources

bioRxiv2024

Tryptophan metabolite atlas uncovers organ, age, and sex-specific variations

Although tryptophan (Trp) is the largest and most structurally complex amino acid, it is the least abundant in the proteome. Its distinct indole ring and high carbon content enable it to generate various biologically active metabolites such as serotonin, kynurenine (Kyn), and indole-3-pyruvate (I3P). Dysregulation of Trp metabolism has been implicated in diseases ranging from depression to cancer. Investigating Trp and its metabolites in healthy tissues offers pathways to target disease-associated disruptions selectively, while preserving essential functions. In this study, we comprehensively mapped Trp metabolites across the Kyn, serotonin, and I3P pathways, as well as the microbiome-derived metabolite tryptamine, in C57BL/6 mice. Our comprehensive analysis covered 12 peripheral organs, the central nervous system, and serum in both male and female mice at three life stages: young (3 weeks), adult (54 weeks), and aged (74 weeks). We found significant tissue-, sex-, and age-specific variations in Trp metabolism, with notably higher levels of the oncometabolites I3P and Kyn in aging males. These findings emphasize the value of organ-specific analysis of Trp metabolism for understanding its role in disease progression and identifying targeted therapeutic opportunities. AUTHOR SUMMARYTrp metabolism has primarily been studied in cell lines, often leading to generalized assumptions about its role in health and disease. However, how Trp and its metabolites are allocated across tissues, sexes, and life stages has remained poorly understood. This gap is critical, as Trp is the largest amino acid, minimally used for protein synthesis, and largely metabolized in the liver, yet its distribution and metabolism in other tissues are unknown. Misconceptions, such as the idea that all cancers universally increase Kyn production, have contributed to therapeutic failures, highlighting the need for rigorous, tissue-specific studies. Our study systematically quantifies Trp metabolites across organs and tissues in vivo, revealing significant organ-, sex-, and age-specific variations. These findings provide a foundational resource for understanding Trp metabolism in normal physiology and disease, with potential applications in cancer, neurodegeneration, and other metabolic disorders.

biochemistry↗

bioRxiv2020

A novel role of MNT as a negative regulator of REL and the NF-κB pathway

MNT, a transcription factor of the MXD family, is an important modulator of the oncoprotein MYC. Both MNT and MYC are basic-helix-loop-helix proteins that heterodimerize with MAX in a mutually exclusive manner, and bind to E-boxes within regulatory regions of their target genes. While MYC generally activates transcription, MNT represses it. However, the molecular interactions involving MNT as a transcriptional regulator beyond the binding to MAX remain unexplored. Here we demonstrate a novel MAX-independent protein interaction between MNT and c-REL (REL), the oncogenic member of the REL/NF-{kappa}B family. REL is involved in important biological processes and it is found altered in a variety of tumors. REL is a transcription factor that remains inactive in the cytoplasm in an inhibitory complex with I{kappa}B and translocates to the nucleus when the NF-{kappa}B pathway is activated. In the present manuscript, we show that MNT knockdown triggers REL translocation into the nucleus and thus the activation of the NF-{kappa}B pathway. Meanwhile, MNT overexpression results in the repression of I{kappa}B, a bona-fide REL target. Indeed, both MNT and REL bind to the I{kappa}B gene at a region mapping in the first exon, suggesting its regulation as a MNT-REL complex. Altogether our data indicate that MNT acts as a repressor of the NF-{kappa}B pathway by two different mechanisms: 1) retention of REL in the cytoplasm by MNT protein interaction and 2) MNT-driven repression of REL-target genes through a MNT-REL complex. These results widen our knowledge about MNT biological roles and reveal a novel connection between the MYC/MXD and the NF-{kappa}B pathways, two of the most prominent pathways involved in cancer.

cancer biology↗

bioRxiv2017

The MYC antagonist MNT autoregulates its expression and supports proliferation in MAX deficient cells

MNT is a transcription factor of the MXD family. MNT-MAX dimers down-regulate genes by binding to E-box sequences, which can also be bound by MYC-MAX to activate transcription. MNT has been described as a modulator of MYC activity but little is known about MNT regulation and whether MNT has MAX-independent functions. Using a MAX deficient cell line and siRNA-mediated silencing of MAX, we show that in the absence of MAX, the total MNT levels are elevated and that MNT localizes both in the cytoplasm and the nucleus. In contrast, MNT is predominantly nuclear when MAX is expressed. MNT is required for optimal cell proliferation even in the absence of MAX, being the first report of a MAX-independent function of MNT. Interestingly, MNT forms homodimers and autoregulates its expression by repressing its own promoter. The tight MNT regulation and its activity in absence of MAX suggest its importance on cell homeostasis.

cancer biology↗