CDKL5 regulates p62-mediated selective autophagy and confers protection against neurotropic viruses.

Virophagy, the selective autophagosomal engulfment and lysosomal degradation of viral components, is crucial for neuronal cell survival and antiviral immunity. However, the mechanisms leading to viral antigen recognition and capture by autophagic machinery remain poorly understood. Here, we identified cyclin-dependent kinase-like 5 (CDKL5), known to function in neurodevelopment, as an essential regulator of virophagy. Loss-of-function mutations in CDKL5 are associated with a severe neurodevelopmental encephalopathy. We found that deletion of CDKL5 or expression of a clinically relevant pathogenic mutant of CDKL5 reduced virophagy of Sindbis virus (SINV), a neurotropic RNA virus, and increased intracellular accumulation of SINV capsid protein aggregates and cellular cytotoxicity. Cdkl5-knockout mice displayed increased viral antigen accumulation and neuronal cell death after SINV infection and enhanced lethality after infection with several neurotropic viruses. Mechanistic studies demonstrated that CDKL5 directly binds the canonical selective autophagy receptor p62 and phosphorylates p62 at T269/S272 to promote its interaction with viral capsid aggregates. We found that CDKL5-mediated phosphorylation of p62 facilitated the formation of large p62 inclusion bodies that captured viral capsids to initiate capsid targeting to autophagic machinery. Overall, these findings identify a cell-autonomous innate immune mechanism for autophagy activation to clear intracellular toxic viral protein aggregates during infection.

Risk factors for the development of active methicillin-resistant Staphylococcus aureus (MRSA) infection in patients colonized with MRSA at hospital admission.

BACKGROUND: Patients who present to Veterans Affairs hospitals are screened for methicillin-resistant Staphylococcus aureus (MRSA) colonization. Those who test positive are isolated during their hospital stay. However, it is unknown which of these patients are most likely to subsequently develop active MRSA infections. METHODS: This retrospective case-control study characterized risk factors for active MRSA infection among patients colonized with MRSA at hospital admission. Potential demographic and clinical risk factors were identified using electronic queries and manual chart abstraction; data were compared by standard statistical tests, and variables with P ≤ .05 in bivariable analysis were entered into a multivariable logistic regression model. RESULTS: There were 71 cases and 213 controls. Risk factors associated with MRSA infection included diabetes mellitus with or without end organ damage (26% vs 14%, P = .02), hemiplegia (9% vs 2%, P = .01), chronic kidney disease (33% vs 20%, P = .03), postcolonization inpatient admission within 90 days (44% vs 29%, P = .03), surgery (41% vs 9%, P < .01), and dialysis (10% vs 3%, P = .02). On multivariable analysis, surgery during follow-up, dialysis during follow-up, and hemiplegia remained significant. CONCLUSIONS: Among patients with MRSA colonization, surgery or dialysis during follow-up and history of hemiplegia were associated with subsequent MRSA infection. Knowledge of these risk factors may allow for future targeted interventions to prevent MRSA infections among colonized patients.

Integrin-mediated first signal for inflammasome activation in intestinal epithelial cells.

How intestinal epithelial cells (IECs) recognize pathogens and activate inflammasomes at intestinal surfaces is poorly understood. We hypothesized that IECs use integrin receptors to recognize pathogens and initiate inflammation within the intestinal tract. We find that IECs infected with Yersinia enterocolitica, an enteric pathogen, use ß1 integrins as pathogen recognition receptors detecting the bacterial adhesin invasin (Inv). The Inv-integrin interaction provides the first signal for NLRP3 inflammasome activation with the type three secretion system translocon providing the second signal for inflammasome activation, resulting in release of IL-18. During infection, Yersinia employs two virulence factors, YopE and YopH, to counteract Inv-mediated integrin-dependent inflammasome activation. Furthermore, NLRP3 inflammasome activation in epithelial cells requires components of the focal adhesion complex signaling pathway, focal adhesion kinase, and rac1. The binding of Inv to ß1 integrins rapidly induces IL-18 mRNA expression, suggesting integrins provide a first signal for NLRP3 inflammasome activation. These data suggest integrins function as pathogen recognition receptors on IECs to rapidly induce inflammasome-derived IL-18-mediated responses.

Mitogen-activated protein kinase-dependent interleukin-1α intracrine signaling is modulated by YopP during Yersinia enterocolitica infection.

Yersinia enterocolitica is a food-borne pathogen that preferentially infects the Peyer's patches and mesenteric lymph nodes, causing an acute inflammatory reaction. Even though Y. enterocolitica induces a robust inflammatory response during infection, the bacterium has evolved a number of virulence factors to limit the extent of this response. We previously demonstrated that interleukin-1α (IL-1α) was critical for the induction of gut inflammation characteristic of Y. enterocolitica infection. More recently, the known actions of IL-1α are becoming more complex because IL-1α can function both as a proinflammatory cytokine and as a nuclear factor. In this study, we tested the ability of Y. enterocolitica to modulate intracellular IL-1α-dependent IL-8 production in epithelial cells. Nuclear translocation of pre-IL-1α protein and IL-1α-dependent secretion of IL-8 into the culture supernatant were increased during infection with a strain lacking the 70-kDa virulence plasmid compared to the case during infection with the wild type, suggesting that Yersinia outer proteins (Yops) might be involved in modulating intracellular IL-1α signaling. Infection of HeLa cells with a strain lacking the yopP gene resulted in increased nuclear translocation of pre-IL-1α and IL-1α-dependent secretion of IL-8 similar to what is observed with bacteria lacking the virulence plasmid. YopP is a protein acetylase that inhibits mitogen-activated protein kinase (MAP kinase)- and NF-κB-dependent signal transduction pathways. Nuclear translocation of pre-IL-1α and IL-1α-dependent secretion of IL-8 in response to Yersinia enterocolitica infection were dependent on extracellular signal-regulated kinase (ERK) and p38 MAP kinase signaling but independent of NF-κB. These data suggest that Y. enterocolitica inhibits intracellular pre-IL-1α signaling and subsequent proinflammatory responses through inhibition of MAP kinase pathways.