Biology subjects

Alvarez, M. I.

Publications and source records attributed to Alvarez, M. I..

3 recordsLinked to original sources

bioRxiv2026

Neuron-specific epigenetic repression of Cdk5 impairs hippocampal-dependent memory in male and female mice

Biological sex regulates fundamental neurobiology, as well as the etiology and prevalence of neuropsychiatric disorders. Cyclin-dependent kinase 5 (Cdk5) is a neuronally enriched kinase that regulates synaptic plasticity, neuronal homeostasis, and hippocampal-dependent memory. While Cdk5 protein activity is necessary and sufficient to promote memory in male rodents, its role in females and its gene regulation in either sex remain poorly understood. In males, Cdk5 protein inhibition impairs fear memory. We previously showed that fear conditioning activates Cdk5 gene expression and increases permissive chromatin acetylation in male, but not female hippocampus. We hypothesize that Cdk5 gene repression would impair fear memory in males. We developed an excitatory neuron-specific, CRISPR/dCas9-HDAC3 epigenetic editing tool to target histone acetylation at the endogenous Cdk5 promoter. This strategy reduced histone acetylation and decreased Cdk5 mRNA, protein, and kinase activity in both sexes. Interestingly, Cdk5 repression in hippocampal neurons impaired fear and spatial memory in both male and female mice. Targeted deacetylation also evicted the transcription factor CREB1 from the Cdk5 promoter, revealing a link between histone acetylation and Cdk5 transcriptional activation. These findings demonstrate that Cdk5 acetylation in neurons is necessary for hippocampal memory in both sexes, providing new insight into sex-specific epigenetic regulation of memory.

molecular biology↗

bioRxiv2020

ARHGEF26 enhances Salmonella invasion and inflammation in cells and mice

Salmonella hijack host machinery in order to invade cells and establish infection. While considerable work has described the role of host proteins in invasion, much less is known regarding how natural variation in these invasion-associated host proteins affects Salmonella pathogenesis. Here we leveraged a candidate cellular GWAS screen to identify natural genetic variation in the ARHGEF26 (Rho Guanine Nucleotide Exchange Factor 26) gene that renders lymphoblastoid cells susceptible to Salmonella Typhi and Typhimurium invasion. Experimental follow-up redefined ARHGEF26s role in Salmonella epithelial cell invasion, identified serovar specific interactions, implicated ARHGEF26 in SopE-mediated invasion, and revealed that the ARHGEF26-associated proteins DLG1 and SCRIB facilitate S. Typhi uptake. Importantly, we show that ARHGEF26 plays a critical role in S. Typhimurium pathogenesis by contributing to bacterial burden in the enteric fever murine model, as well as inflammation in the gastroenteritis infection model. The impact of ARHGEF26 on inflammation was also seen in cells, as knockdown reduced IL-8 production in HeLa cells. Together, these data reveal pleiotropic roles for ARHGEF26 function during infection and highlight that many of the interactions that occur during infection that are thought to be well understood likely have underappreciated complexity. Author SummaryDuring infection, Salmonella manipulates host cells into engulfing the bacteria and establishing an intracellular niche. While many studies have identified genes involved in different stages of this Salmonella invasion process, few studies have examined how differences between human hosts contribute to infection susceptibility. Here we leveraged a candidate genetic screen to identify natural genetic variation in the human ARHGEF26 gene that correlates with Salmonella invasion. Springboarding from this result, we experimentally tested and revised existing models of ARHGEF26s role in Salmonella invasion, discovered an additional new role for ARHGEF26 during Salmonella disease, and confirmed our findings in mouse models. Building on how ARHGEF26 functions in other contexts, we implicated two ARHGEF26-interacting host proteins as contributors to Salmonella pathobiology. Collectively, these results identify a potential source of inter-person diversity in susceptibility to Salmonella disease, expand our molecular understanding of Salmonella infection to include a multifaceted role for ARHGEF26, and identify several important future directions that will be important to understand how Salmonella recruit and manipulate ARHGEF26 as well as how ARHGEF26 is able to drive Salmonella-beneficial processes.

microbiology↗

bioRxiv2019

Pathogen-encoded evasion of CXCL10 and T cell responses

Clearance of intracellular pathogens, such as Leishmania (L.) major, depends on a well-regulated adaptive T cell response. Here we describe a pathogen-encoded mechanism to alter T cell recruitment by suppressing CXCL10, a chemokine that recruits CD4+ and CD8+ T cells by signaling through the CXCR3 receptor. L. major suppresses CXCL10 through the virulence factor and protease, glycoprotein-63 (gp63). GP63 cleaves CXCL10 after amino acid A81, impairing T-cell chemotaxis in vitro. GP63 from either extracellular promastigotes or intracellular amastigotes is capable of cleaving CXCL10. Consistent with CXCL10 cleavage during infection, we observed GP63-mediated impairment of activated CD8+ T-cells in the draining lymph nodes of C57BL/6JWT mice. Correspondingly, in C57BL/6JWT mice, gp63 deletion resulted in slower lesion development and a smaller maximum lesion size. However, infection in C57BL/6Jcxcr3-/- mice revealed the delay to lesion development required CXCR3 signaling. Finally, Salmonella enterica and Chlamydia trachomatis infection also suppress CXCL10, demonstrating convergent evolution of this immune evasion strategy in diverse intracellular pathogens. Understanding mechanisms of CXCL10 evasion may facilitate the development of novel therapeutic strategies to treat intracellular pathogens. Author SummaryLeishmaniasis is an infectious disease that affects over one million people annually. It is caused by intracellular parasites that have evolved to evade the hosts attempts to eliminate the parasite. The most common form of disease, cutaneous leishmaniasis, causes disfiguring skin lesions if the host immune system does not appropriately respond to the infection. A family of molecules called chemokines are critical for the recruitment of specific subsets of immune cells required to eliminate infection. Here, we demonstrate a novel mechanism that the parasite Leishmania (L.) major employs to disrupt the immune response by interfering with chemokine signaling. By this strategy, L. major uses a protease to cleave chemokines known to recruit T-cells required for fighting off infection. We show that L. major cleavage of these immune signals changes the recruitment of CD8+ T-cells and alters disease progression in mice. Finally, we observe that multiple common human intracellular pathogens, including Chlamydia trachomatis and Salmonella enterica, interfere with the same chemokines, suggesting a strong selective pressure to avoid this component of the immune response. Our study provides new insights into how intracellular pathogens interact with the host immune response to enhance pathogen survival and exacerbate disease outcomes.

microbiology↗