Biology subjects

Gutierrez, M. A.

Publications and source records attributed to Gutierrez, M. A..

8 recordsLinked to original sources

bioRxiv2025

A novel plasmid-mediated PAC β-lactamase (PAC-2) variant confers resistance to ceftazidime-avibactam in Klebsiella quasipneumoniae ST526, in Colombia.

Globally, the increasing reports of resistance to ceftazidime-avibactam (CZA) in Enterobacterales are concerning. In this paper we describe an isolate of Klebsiella quasipneumoniae (GMR-RA-2034.23) highly resistant to ceftazidime-avibactam, ceftolozane-tazobactam, ceftazidime and cefotaxime in which a new variant of the PAC {beta}-lactamase, designated PAC-2 by the NCBI, was identified. The blaPAC-2 gene is encoded in a non-conjugative plasmid type IncQ (9,452 bp). The GMR-RA-2034.23 isolate did not present mutations in the OmpK35 or OmpK36 porins, associated with resistance to CZA. This is the first description of PAC-type {beta}-lactamase in Colombia. Continuous monitoring of mechanisms of resistance to CZA is crucial to prevent its spread.

microbiology↗

bioRxiv2024

Tracing the stepwise Darwinian evolution of a plant halogenase

Halogenation chemistry is rare in plant metabolism, with the chloroalkaloid acutumine produced by Menispermaceae species being the only well characterized example, involving a specialized dechloroacutumine halogenase (DAH) from the iron(II)- and 2-oxoglutarate-dependent dioxygenase (2ODD) superfamily. While DAH is presumed to have evolved from an ancestral 2ODD enzyme, the broader question of how new enzymes arise through Darwinian processes, such as the birth of DAH in Menispermaceae, remains a fundamental challenge in understanding metabolic evolution. Here, we investigate DAHs evolutionary trajectory using the chromosomal-level genome assembly of Menispermum canadense. By analyzing the genomic context of DAH in M. canadense and syntenic regions in related plants, we show that DAH evolved through tandem duplication of an ancestral flavonol synthase (FLS) gene, followed by a series of neofunctionalization and gene loss events. Through structural modeling, molecular dynamics simulations, and site-directed mutagenesis, we identify residue changes enabling the transition from FLS to DAH. This functional switch required traversing a complex evolutionary landscape where adaptive peaks were separated by deep fitness valleys. Our work illustrates how new enzymatic functions can arise through lineage-specific evolutionary pathways that gradually reshape the active site architecture through permissive mutations, ultimately enabling mechanism-switching mutations that establish novel catalytic activities.

biochemistry↗

bioRxiv2024

They all rock: A systematic comparison of conformational movements in LeuT-fold transporters

Many membrane transporters share the LeuT fold--two five-helix repeats inverted across the membrane plane. Despite hundreds of structures, whether distinct conformational mechanisms are supported by the LeuT fold has not been systematically determined. After annotating published LeuT-fold structures, we analyzed distance difference matrices (DDMs) for nine proteins with multiple available conformations. We identified rigid bodies and relative movements of transmembrane helices (TMs) during distinct steps of the transport cycle. In all transporters the bundle (first two TMs of each repeat) rotates relative to the hash (third and fourth TMs). Motions of the arms (fifth TM) to close or open the intracellular and outer vestibules are common, as is a TM1a swing, with notable variations in the opening-closing motions of the outer vestibule. Our analyses suggest that LeuT-fold transporters layer distinct motions on a common bundle-hash rock and demonstrate that systematic analyses can provide new insights into large structural datasets.

biophysics↗

bioRxiv2021

Stabilization of Microbial Communities by Responsive Phenotypic Switching

Clonal microbes can switch between different phenotypes and recent theoretical work has shown that stochastic switching between these subpopulations can stabilize microbial communities. This phenotypic switching need not be stochastic, however, but could also be in response to environmental factors, both biotic and abiotic. Here, motivated by the bacterial persistence phenotype, we explore the ecological effects of such responsive switching by analyzing phenotypic switching in response to competing species. We show that the stability of microbial communities with responsive switching differs generically from that of communities with stochastic switching only. To understand the mechanisms by which responsive switching stabilizes coexistence, we go on to analyze simple two-species models. Combining exact results and numerical simulations, we extend the classical stability results for the competition of two species without phenotypic variation to the case in which one species switches, stochastically and responsively, between two phenotypes. In particular, we show that responsive switching can stabilize coexistence even when stochastic switching on its own does not affect the stability of the community.

biophysics↗

bioRxiv2021

Tubulinopathy mutations in TUBA1A that disrupt neuronal morphogenesis and migration override XMAP215/Stu2 regulation of microtubule dynamics

Heterozygous, missense mutations in - or {beta}-tubulin genes are associated with a wide range of human brain malformations, known as tubulinopathies. We seek to understand whether a mutations impact at the molecular and cellular levels scale with the severity of brain malformation. Here we focus on two mutations at the valine 409 residue of TUBA1A, V409I and V409A, identified in patients with pachygyria or lissencephaly, respectively. We find that ectopic expression of TUBA1A-V409I/A mutants disrupt neuronal migration in mice and promote excessive neurite branching and delayed retraction in primary neuronal cultures, accompanied by increased microtubule acetylation. To determine the molecular mechanisms, we modeled the V409I/A mutants in budding yeast and found that they promote intrinsically faster microtubule polymerization rates in cells and in reconstitution experiments with purified tubulin. In addition, V409I/A mutants decrease the recruitment of XMAP215/Stu2 to plus ends and ablate tubulin binding to TOG domains. In each assay tested, the TUBA1A-V409I mutant exhibits an intermediate phenotype between wild type and the more severe TUBA1A-V409A, reflecting the severity observed in brain malformations. Together, our data support a model in which the V409I/A mutations may limit tubulin conformational states and thereby disrupt microtubule regulation during neuronal morphogenesis and migration.

cell biology↗

bioRxiv2020

Csmd2 interacts with Dab1 and is Required in Reelin-Mediated Neuronal Maturation

Reelin is a glycoprotein secreted by Cajal-Retzius cells to regulate development of the cerebral cortex. Reelin binding to its receptors on immature neurons initiates a signaling cascade through the downstream adaptor protein, Dab1. Defects in this signaling mechanism result in perturbed neuronal migration, reductions in dendrite complexity, and deficits in synapse development and function. How Reelin controls neuronal migration and brain lamination have been extensively investigated over the years, but the pathways that regulate dendrite and spine development downstream of Reelin and Dab1 have yet to be fully elucidated. Here, we have identified a novel interaction between Dab1 and Csmd2, a synaptic transmembrane protein required for dendrite and dendritic spine development in forebrain excitatory neurons. We demonstrate that Csmd2 contains an NPxY motif on its intracellular region, through which Dab1 interacts with Csmd2. Interestingly, we find that this NPxY consensus motif is not required for Csmd2 to localize at the postsynaptic densities of spiny neurons. Rather, the introduction of an NPxY mutant form of Csmd2 results in a significant overproduction of immature, filopodia-like dendritic spines in maturing neurons. Moreover, we show that knockdown of Csmd2 mRNA expression in immature developing neurons abolishes the ability of Reelin to promote dendrite elaboration and dendritic spine maturation. This suggests that the Csmd2-Dab1 interaction may be a requirement of Reelin/Dab1 signaling to mediate the structural maturation of neurons. Together, these results point toward a role of Csmd2 in the Reelin/Dab1 signaling axis that promotes the development of dendrites and dendritic spines in maturing neurons. Summary StatementHow Reelin controls neuronal maturation remains to be understood. We demonstrate that the synaptic protein Csmd2 interacts with the Reelin-associated adaptor protein Dab1. We also determine that Reelin requires Csmd2 to regulate structural development and maturation of forebrain neurons.

neuroscience↗

bioRxiv2019

The Insulin Receptor In Astrocytes Is Involved In The Entrance Of Circulating Insulin Into The Brain

Circulating insulin enters into the brain through mechanisms that are not yet entirely understood. We now report that mice lacking insulin receptors (IR) in astrocytes show reduced uptake of circulating insulin and blunted brain responses to this circulating hormone, suggesting that astrocytes form part of the cellular pathway in the entrance of circulating insulin into the brain. Since we previously showed that ablation of IR in astrocytes decreases brain glucose uptake, we conclude that astrocytic IRs regulate uptake of circulating glucose and insulin.

neuroscience↗

bioRxiv2018

Csmd2 is a Synaptic Transmembrane Protein that Interacts with PSD-95

Mutations and copy number variants of the Cub and Sushi Multiple Domains 2 (CSMD2) gene are associated with schizophrenia and autism spectrum disorder. CSMD2 is a single-pass transmembrane protein with a large extracellular domain comprising repeats of Cub and Sushi domains. Although the biological functions of CSMD2 have not been studied, the association between CSMD2 variants and cognitive function suggest that it may have a role in brain development or function. In this study, we show that mouse Csmd2 is expressed in excitatory and inhibitory neurons in the brain. Csmd2 protein exhibits a somatodendritic localization in the neocortex and hippocampus, with smaller puncta localizing further out in the neuropil. We show that many of these Csmd2 puncta co-localize with the synaptic protein PSD-95. Using immunohistochemical and biochemical methods, we further demonstrate that Csmd2 localizes to dendritic spines and is enriched in the postsynaptic density. We also find Csmd2 at ribbon synapses of the inner plexiform layer of the retina, suggesting a broader synaptic function of Csmd2 in the central nervous system. Finally, we show that the cytoplasmic tail domain of Csmd2 interacts with synaptic scaffolding proteins of the membrane-associated guanylate kinase (MAGUK) family. The association between Csmd2 and MAGUK member PSD-95 is dependent on a PDZ-binding domain on the Csmd2 tail, which is also required for synaptic targeting of Csmd2. Together, these results point toward a function for Csmd2 in dendrites and synapses, which may account for its association with several psychiatric disorders.

cell biology↗