Biology subjects

Valenzuela, S.

Publications and source records attributed to Valenzuela, S..

4 recordsLinked to original sources

bioRxiv2023

Resin acids play key roles in shaping microbial communities during degradation of spruce bark

The bark is the outermost defense of trees against microbial attack, largely thanks to toxicity and prevalence of extractive compounds. Nevertheless, bark decomposes in nature, though by which species and mechanisms remains unknown. Here, we have followed the development of microbial enrichments growing on spruce bark over six months, by monitoring both chemical changes in the material and performing community and metagenomic analyses. Carbohydrate metabolism was unexpectedly limited, and instead a key activity was metabolism of extractives. Resin acid degradation was principally linked to community diversification with specific bacteria revealed to dominate the process. Metagenome-guided isolation facilitated the recovery of the dominant enrichment strain in pure culture, which represents a new species (Pseudomonas abieticivorans sp. nov.), that can grow on resin acids as a sole carbon source. Our results illuminate key stages in degradation of an abundant renewable resource, and how defensive extractive compounds have major roles in shaping microbiomes.

microbiology↗

bioRxiv2020

In vivo and in vitro mechanistic characterization of a clinically relevant PolγA mutation

Mutations in POLG, encoding POL{gamma}A, the catalytic subunit of the mitochondrial DNA polymerase, cause a spectrum of disorders characterized by mtDNA instability. However, the molecular pathogenesis of POLG-related diseases is poorly understood and efficient treatments are missing. Here, we generated a POLGA449T/A449T mouse model, which reproduces the most common human recessive mutation of POLG, encoding the A467T change, and dissected the mechanisms underlying pathogenicity. We show that the A449T mutation impairs DNA binding and mtDNA synthesis activities of POL{gamma} in vivo and in vitro. Interestingly, the A467T mutation also strongly impairs interactions with POL{gamma}B, the homodimeric accessory subunit of holo-POL{gamma}. This allows the free POL{gamma}A to become a substrate for LONP1 protease degradation, leading to dramatically reduced levels of POL{gamma}A, which in turn exacerbates the molecular phenotypes of PolgA449T/A449T mice. Importantly, we validated this mechanism for other mutations affecting the interaction between the two POL{gamma} subunits. We suggest that LONP1 dependent degradation of POL{gamma}A can be exploited as a target for the development of future therapies.

genetics↗

bioRxiv2020

Structural and molecular determinants of CCS-mediated copper activation of MEK1/2

SummaryNormal physiology relies on the precise coordination of intracellular signal transduction pathways that respond to nutrient availability to balance cell growth and cell death. We recently established a critical mechanistic function for the redox-active micronutrient copper (Cu) in the canonical mitogen activated protein kinase (MAPK) pathway at the level of MEK1 and MEK2. Here we report the X-ray crystal structure of Cu-MEK1 and reveal active site chemical ligands and oxidation state specificity for MEK1 Cu coordination. Mechanistically, the Cu chaperone CCS selectively bound to and facilitated Cu transfer to MEK1. Mutations in MEK1 that disrupt Cu(I) affinity or a CCS small molecule inhibitor reduced Cu-stimulated MEK1 kinase activity. These atomic and molecular level data provide the first mechanistic insights of Cu kinase signaling and could be exploited for the development of novel MEK1/2 inhibitors that either target the Cu structural interface or blunt dedicated Cu delivery mechanisms via CCS.Competing Interest StatementD.C.B holds ownership in Merlon Inc. D.C.B. is an inventor on the patent application 20150017261 entitled Methods of treating and preventing cancer by disrupting the binding of copper in the MAP kinase pathway. No potential conflicts of interest were disclosed by the other authors.View Full Text

biochemistry↗

bioRxiv2017

Versatile Multicolor Nanodiamond Probes for Intracellular Imaging and Targeted Labeling

Diamond nanoparticles that host bright luminescent centers are attracting attention for applications in bio-labeling and bio-sensing. Beyond their unsurpassed photostability, diamond can host multiple color centers, from the blue to the near infra-red spectral range. While nanodiamonds hosting nitrogen vacancy defects have been widely employed as bio-imaging probes, production and fabrication of nanodiamonds with other color centers is a challenge. In this work, a large scale production of fluorescent nanodiamonds (FNDs) containing a near infrared (NIR) color center - namely the silicon vacancy (SiV) defect, is reported. More importantly, a concept of application of different color centers for multi-color bio-imaging to investigate intercellular processes is demonstrated. Furthermore, two types of FNDs within cells can be easily resolved by their specific spectral properties, where data shows that SiV FNDs initially dispersed throughout the cell interior while NV FNDs localized in a close proximity to nucleus. The reported results are the first demonstration of multi-color labeling with FNDs that can pave the way for the wide-ranging use of FNDs in applications, including bio-sensing, bio-imaging and drug delivery applications.

biochemistry↗