Biology subjects

Guerrero, C.

Publications and source records attributed to Guerrero, C..

3 recordsLinked to original sources

bioRxiv2023

SARS-CoV-2 infection is associated with intestinal permeability, systemic inflammation, and microbial dysbiosis in hospitalized COVID-19 patients

Coronavirus disease 2019 (COVID-19) and associated severity has been linked to uncontrolled inflammation and may be associated with changes in the microbiome of mucosal sites including the gastrointestinal tract and oral cavity. These sites play an important role in host-microbe homeostasis and disruption of epithelial barrier integrity during COVID-19 may potentially lead to exacerbated inflammation and immune dysfunction. Outcomes in COVID-19 are highly disparate, ranging from asymptomatic to fatal, and the impact of microbial dysbiosis on disease severity is unclear. Here, we obtained plasma, rectal swabs, oropharyngeal swabs, and nasal swabs from 86 patients hospitalized with COVID-19 and 12 healthy volunteers. We performed 16S rRNA sequencing to characterize the microbial communities in the mucosal swabs and measured circulating cytokines, markers of gut barrier integrity, and fatty acids in the plasma samples. We compared these plasma concentrations and microbiomes between healthy volunteers and the COVID-19 patients who had survived or unfortunately died by the end of study enrollment, and between severe disease and healthy controls, as well as performed a correlation analysis between plasma variables and bacterial abundances. The rectal swabs of COVID-19 patients had reduced abundances of several commensal bacteria including Faecalibacterium prausnitsii, and an increased abundance of the opportunistic pathogens Eggerthella lenta and Hungatella hathewayi. Furthermore, the oral pathogen Scardovia wiggsiae was more abundant in the oropharyngeal swabs of COVID-19 patients who died. The abundance of both H. hathewayi and S. wiggsiae correlated with circulating inflammatory markers including IL-6, highlighting the possible role of the microbiome in COVID-19 severity, and providing potential therapeutic targets for managing COVID-19.

microbiology↗

bioRxiv2022

Crk proteins activate the Rap1 guanine nucleotide exchange factor C3G by segregated adaptor-dependent and -independent mechanisms

C3G is a guanine nucleotide exchange factor (GEF) that activates Rap1 to promote cell adhesion. Resting C3G is autoinhibited and the GEF activity is released by stimuli that signal through tyrosine kinases. Tyrosine phosphorylation of C3G and interaction with Crk adaptor proteins, whose expression is increased in multiple human cancers, participate in C3G activation. However, the molecular details of C3G activation and the interplay between C3G phosphorylation and Crk interaction are poorly understood. Here, we combine biochemical, biophysical, and cell biology approaches to elucidate the mechanisms of C3G activation. CrkL interacts through its SH3N domain with the proline-rich motifs P1 and P2 of inactive C3G in vitro and in Jurkat and HEK293T cells, and these sites are necessary to recruit C3G to the plasma membrane. However, direct stimulation of the GEF activity requires binding of Crk proteins to the P3 and P4 sites. P3 is occluded in resting C3G and is essential for activation, while P4 contributes secondarily towards complete stimulation. Tyrosine phosphorylation of C3G alone causes marginal activation. Instead, phosphorylation primes C3G lowering the concentration of Crk proteins required for activation and increasing the maximum activity. Unexpectedly, optimal activation also requires the interaction of CrkL-SH2 domain with phosphorylated C3G. Phosphorylation and Crk-binding form a two-factor mechanism that ensures tight control of C3G activation. The simultaneous SH2 and SH3N interaction of CrkL with C3G, required for the activation, reveals a novel adaptor-independent function of Crk proteins relevant to understanding their role in physiological signaling and their deregulation in diseases.

molecular biology↗

bioRxiv2022

Upregulation of TLR4/MyD88 pathway in alcohol-induced Wernicke's encephalopathy: findings in preclinical models and in a postmortem human case

Wernickes encephalopathy (WE) is a neurologic disease caused by vitamin B1 or thiamine deficiency (TD), being the alcohol use disorder (AUD) its main risk factor. WE patients present limiting motor, cognitive and emotional alterations related to a selective cerebral vulnerability. Neuroinflammation has been proposed as one of the phenomena contributing to brain damage. Our previous studies provide evidence for the involvement of the innate immune receptor Toll-like (TLR) 4 in the inflammatory response induced in the frontal cortex and cerebellum in TD animal models (animals fed with TD diet and receiving pyrithiamine). However, the effects of the combination of chronic alcohol consumption and TD on TLR4 and their specific contribution to the pathogenesis of WE are currently unknown. Additionally, no studies on TLR4 have been conducted on WE patients since brains from these patients are difficult to achieve. Here, we used rat models of chronic alcohol (CA; 9 months of forced consumption of 20% (w/v) alcohol), TD hit (TDD; TD diet + daily 0.25 mg/kg i.p. pyrithiamine during 12 days), or a combined treatment (CA+TDD) to check the activation of the proinflammatory TLR4/MyD88 pathway and related markers in the frontal cortex and the cerebellum. In addition, we characterized for the first time the TLR4 and its co-receptor MyD88 signature, along with other markers of this proinflammatory signaling such as phospo-NF{kappa}B p65 and I{kappa}B, in the post-mortem human frontal cortex and cerebellum (gray and white matter) of an alcohol-induced WE patient, comparing it with negative (no disease) and positive (aged brain with Alzheimers disease) control subjects for neuroinflammation. We found an increase in the cortical TLR4 and its adaptor molecule MyD88, together with an upregulation of the proinflammatory signaling molecules p-NF-B and IB in the CA+TDD animal model. In the patient diagnosed with alcohol-induced WE we observed cortical and cerebellar upregulation of the TLR4/MyD88 pathway. Thus, our findings provide evidence, both in the animal model and the human postmortem brain, of the upregulation of the TLR4/MyD88 proinflammatory pathway in WE related to alcohol consumption.

neuroscience↗