Biology subjects

Sanchez, M. A.

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

7 recordsLinked to original sources

bioRxiv2026

Transition Fibers Play a Central Role in Import of a Glucose Transporter into the Flagellar Membrane

Leishmania parasite promastigotes have a motile flagellum that encompasses a variety of integral membrane proteins, but how such proteins traffic selectively to the flagellum is largely unknown. The flagellar-specific glucose transporter, GT1, binds to the KHARON protein via the transporter hydrophilic amino terminal domain, and KHARON is essential for trafficking of GT1 from the flagellar pocket membrane at the base of the flagellum into the flagellar membrane. A major objective of this study was to determine the mechanism whereby KHARON transports GT1 into the flagellar membrane. We have determined that KHARON is a novel component of the transition fibers that project from the basal body at the base of the flagellum toward the flagellar membrane. We propose that KHARON binds GT1 at the transition fibers and then transfers it to intraflagellar transport (IFT) trains as they enter the flagellum at this site. The IFT trains, associated with the membrane tethering protein TULP, then move GT1 through the transition zone filter into the body of the flagellum. These results provide evidence for a role for transition fibers in transport of membrane proteins into flagella.

cell biology↗

bioRxiv2025

Kazal-type serine protease inhibitors from Arabidopsis thaliana and Toxoplasma gondii exhibit antimicrobial activity against plant pathogens

Kazal-type serine protease inhibitors (KPIs) interfere with microbial proteases and have been associated with antimicrobial activity, yet their specific role in plant protection remains poorly understood. In this work, we evaluated the antimicrobial potential of recombinant Arabidopsis thaliana KPI (rAtKPI-1T), recombinant Toxoplasma gondii KPI (rTgPI-1), and two truncated versions of rTgPI-1 (rTgPI-1NT and rTgPI-1CT). Both rAtKPI-1T and rTgPI-1 exhibited inhibitory effects against Pseudomonas syringae DC3000, P. syringae (AvRpm1), and P. viridiflava in a concentration-dependent manner, with significant inhibition at 3.5 M. The lower MIC50 values obtained for rTgPI-1 and its truncated forms compared to rAtKPI-1T suggest a higher antibacterial potency. Binding and immunofluorescence assays further revealed that rAtKPI-1T, rTgPI-1, and rTgPI-1NT associated with bacterial surfaces, while rTgPI-1CT displayed weaker or transient interactions. In addition to their antibacterial activity, rTgPI-1NT and rTgPI-1CT also inhibited the germination of Botrytis cinerea conidia. Both truncated proteins significantly reduced germination after 6 and 9 hours of incubation, with rTgPI-1CT exerting a markedly stronger antifungal effect than rTgPI-1NT. These findings suggest that specific Kazal-type domains, particularly those in the C-terminal region, could play a critical role in suppressing early infection processes of necrotrophic fungi. Overall, this study demonstrates that rKPIs display distinct and complementary antimicrobial profiles mediated by microbial binding and protease inhibition. The contrasting activities of rTgPI-1NT and rTgPI-1CT highlight the value of domain-level analysis to discern functional contributions within multidomain KPIs. These results expand current knowledge on plant-derived protease inhibitors and underscore their potential as biotechnological tools for sustainable crop protection.

microbiology↗

bioRxiv2025

Striatal pathways oppositely shift cortical activity along the decision axis

The cortex and basal ganglia are organized into multiple parallel loops that serve motor, limbic, and cognitive functions. The classic model of cortico-basal ganglia interactions posits that within each loop, the direct pathway of the basal ganglia activates the cortex and the indirect pathway inhibits it1-3. While this model has found support in the motor domain4,5, whether opponent control by the two pathways extends to the cognitive domain remains unknown. Here, we record from anterior cingulate cortex (ACC) and dorsomedial striatum (DMS) while inhibiting direct or indirect pathway neurons in DMS, as mice perform an accumulation-of-evidence task6-10. Inconsistent with the classic model, the manipulations do not produce opponent changes in overall ACC activity. Instead, the pathways exert opponent influence over a subpopulation of ACC neurons that encode accumulated sensory evidence, the task-relevant decision variable. The direction of the modulation depends on a neurons tuning to ipsilateral versus contralateral evidence, such that the two pathways generate opponent shifts in coding specifically along the decision axis. Thus, our results uncover unexpected specificity in the effects of basal ganglia pathways on the cortex, with the two pathways of the DMS exerting opponent control not on overall activity but on coding of the relevant task variable. This functional specificity may extend to other basal ganglia loops to support different aspects of adaptive behavior, with the pathways serving a general role in selecting and shifting cortical representations to subserve circuit-specific functions.

neuroscience↗

bioRxiv2023

Safe plant Hsp90 adjuvants elicit an effective immune response against SARS-CoV2 derived RBD antigen

To better understand the role of pHsp90 adjuvant in immune response modulation, we proposed the use of the Receptor Binding Domain (RBD) of the Spike protein of SARS-CoV2, the principal candidate in the design of subunit vaccines. We evaluated the humoral and cellular immune responses against RBD through the strategy "protein mixture" (Adjuvant + Antigen). The rRBD adjuvanted with rAtHsp81.2 group showed a higher increase of the anti-rRBD IgG1, while the rRBD adjuvanted with rNbHsp90.3 group showed a significant increase of anti-rRBD IgG2b/2a. These results were consistent with the cellular immune response analysis. Spleen cell cultures from rRBD+rNbHsp90.3-immunized mice showed significantly increased IFN-{gamma} production. In contrast, spleen cell cultures from rRBD+rAtHsp81.2-immunized mice showed significant increased IL-4 levels. Finally, vaccines adjuvanted with rNbHsp90.3 induced higher neutralizing antibody responses compared to those adjuvanted with rAtHsp81.2. To know whether both chaperones must form complexes to generate an effective immune response, we performed co-immunoprecipitation (co-IP) assays. The results indicated that the greater neutralizing capacity observed in the rRBD adjuvanted with rNbHsp90.3 group would be given by the rRBD-rNbHsp90.3 interaction rather than by the quality of the immune response triggered by the adjuvants. These results, together with our previous results, provide a comparative benchmark of these two novel and safe vaccine adjuvants for their capacity to stimulate immunity to a subunit vaccine, demonstrating the capacity of adjuvanted SARS-CoV2 subunit vaccines. Furthermore, these results revealed differences in the ability to modulate the immune response between these two pHsp90s, highlighting the importance of adjuvant selection for future rational vaccine and adjuvant design.

molecular biology↗

bioRxiv2022

Root organogenesis induction in Epipremnum aureum stem cuttings with plant biostimulants and synthetic rooting hormone

Plant organogenesis induction is a vital method to regenerate explants and produce complete organisms. In this study, we analyzed the applicability of three different root biostimulants and a commercially available synthetic rooting hormone (RH) for root organogenesis induction in Epipremnum aureum stem cuttings. The biostimulants used were Aloe vera gel (AV1), and garlic (GR2) and turmeric extracts (TM3), and the synthetic RH (TakeRoot(R)) used contained an active ingredient, indole butyric acid (0.01%). The E. aureum stem cuttings were placed in hydroponic pots and root development rates were monitored for up to 30 days. Recorded data from five parameters were analyzed: (1) number of rooted cuttings, (2) number of roots per stem cutting, (3) length of the longest and (4) shortest roots of the cuttings, and (5) rooting time. Stem cuttings were quantified using ImageJ software. The results showed that compared to the application of TakeRoot(R), treatment with the biostimulant AV1 produced the longest roots, whereas stem cuttings treated with GR2 and TM3 did not produce significant results. Moreover, AV1 induced root organogenesis 16.67% faster than did TakeRoot(R) but no significant difference (p<0.05) was observed in the case of number of roots promoted per cutting. This study provides scientific evidence for the application of naturally derived RHs in the propagation of stem cuttings. Furthermore, Aloe vera gel, known for plant growth benefits, is the best choice for plant root propagation.

plant biology↗

bioRxiv2020

The Trypanosoma brucei Cytoskeletal Protein KHARON Associates with Partner Proteins to Mediate Both Cytokinesis and Trafficking of Flagellar Membrane Proteins

In the African trypanosome Trypanosoma brucei, the cytoskeletal protein TbKHARON is required for trafficking of a putative Ca2+ channel to the flagellar membrane, and it is essential for parasite viability in both the mammalian stage bloodstream forms and the tsetse fly procyclic forms. This protein is located at the base of the flagellum, in the pellicular cytoskeleton, and in the mitotic spindle in both life cycle forms, and it likely serves multiple functions for these parasites. To begin to deconvolve the functions of KHARON, we have investigated partners associated with this protein and their roles in parasite biology. One KHARON associated protein, TbKHAP1, is a close interaction partner that can be crosslinked to KHARON by formaldehyde and pulled down in a molecular complex, and it colocalizes with TbKHARON in the basal body at the base of the flagellum. Knockdown of TbKHAP1 mRNA has similar phenotypes to knockdown of its partner TbKHARON, impairing trafficking of the Ca2+ channel to the flagellar membrane and blocking cytokinesis, implying that the TbKHARON/TbKHAP1 complex mediates trafficking of flagellar membrane proteins. Two other KHAPs, TbKHAP2 and TbKHAP3, are in close proximity to TbKHARON, but knockdown of their mRNAs does not affect trafficking of the Ca2+ channel. Two different flagellar membrane proteins, which are extruded from the flagellar membrane into extracellular vesicles, are also dependent upon TbKHARON for flagellar trafficking. These studies confirm that TbKHARON acts in complexes with other proteins to carry out various biological functions, and that some partners are involved in the core activity of targeting membrane proteins to the flagellum.

cell biology↗

bioRxiv2020

A Cytoskeletal Protein Complex is Essential for Division of Intracellular Amastigotes of Leishmania mexicana

Previous studies in Leishmania mexicana have identified the cytoskeletal protein KHARON as being important for both flagellar trafficking of the glucose transporter GT1 and for successful cytokinesis and survival of infectious amastigote forms inside mammalian macrophages. KHARON is located in three distinct regions of the cytoskeleton: the base of the flagellum, the subpellicular microtubules, and the mitotic spindle. To deconvolve the different functions for KHARON, we have identified two partner proteins, KHAP1 and KHAP2, that associate with KHARON. KHAP1 is located only in the subpellicular microtubules, while KHAP2 is located at the subpellicular microtubules and the base of the flagellum. Both the KHAP1 and KHAP2 null mutants are unable to execute cytokinesis but are able to traffic GT1 to the flagellum. These results confirm that KHARON assembles into distinct functional complexes and that the subpellicular complex is essential for cytokinesis and viability of disease-causing amastigotes but not for flagellar membrane trafficking.

microbiology↗