Microbiota-Derived Short-Chain Fatty Acids Promote LAMTOR2-Mediated Immune Responses in Macrophages

ABSRTACTKlebsiella pneumoniae is a common cause of human-pneumonia-derived sepsis with high morbidity and mortality. The microbiota promotes and maintains host immune homeostasis. The mechanisms by which the gut microbiota affects the host defenses in the respiratory system systematically, however, remain poorly understood. Here, we show that gut microbiota depletion increases susceptibility to extracellular K. pneumoniae infections in terms of increased bacterial burdens in lung and decreased survival rates. Oral supplementation with gut microbiota-derived short-chain fatty acids (SCFAs), subsequently activating G protein-coupled receptor 43 (GPCR43), enhances a macrophage's capacity to phagocytose invading K. pneumoniae Furthermore, SCFAs and GPR43 increase macrophage bacterial clearance by upregulating LAMTOR2, which is further identified as an antibacterial effector and elucidated to facilitate phagosome-lysosome fusion and extracellular signal-regulated kinase (ERK) phosphorylation. Lastly, conditional ablation of Lamtor2 in macrophages decreases their antimicrobial activity, even though mice were pretreated with exogenous SCFA supplementation.IMPORTANCE These observations highlight that SCFAs promote macrophage elimination of K. pneumoniae via a LAMTOR2-dependent signal pathway and suggest that it is possible to intervene in K. pneumoniae pneumonia by targeting the gut microbiota.

LAMTOR2 (p14) Controls B Cell Differentiation by Orchestrating Endosomal BCR Trafficking

B-cell development and function depend on stage-specific signaling through the B-cell antigen receptor (BCR). Signaling and intracellular trafficking of the BCR are connected, but the molecular mechanisms of this link are incompletely understood. Here, we investigated the role of the endosomal adaptor protein and member of the LAMTOR/Ragulator complex LAMTOR2 (p14) in B-cell development. Efficient conditional deletion of LAMTOR2 at the pre-B1 stage using mb1-Cre mice resulted in complete developmental arrest. Deletion of LAMTOR2 using Cd19-Cre mice permitted analysis of residual B cells at later developmental stages, revealing that LAMTOR2 was critical for the generation and activation of mature B lymphocytes. Loss of LAMTOR2 resulted in aberrant BCR signaling due to delayed receptor internalization and endosomal trafficking. In conclusion, we identify LAMTOR2 as critical regulator of BCR trafficking and signaling that is essential for early B-cell development in mice.

Familial 1q22 microduplication associated with psychiatric disorders, intellectual disability and late-onset autoimmune inflammatory response

Background

Despite the extensive use of chromosomal microarray technologies in patients with neurodevelopmental disorders has permitted the identification of an increasing number of causative submicroscopic rearrangements throughout the genome, constitutional duplications involving chromosome 1q22 have seldom been described in those patients.

Results

We report on a pedigree with seven affected members showing varying degrees of behavioural and emotional disturbances including general anxiety disorder, mood disorders, and intellectual disability. Two adult female patients also showed late onset autoimmune inflammatory responses characterized by alopecia, skin ulcers secondary to inflammatory vasculitis, interstitial lung disease, and Raynaud’s phenomenon. Array-CGH analysis identified in the affected individuals a 290 Kb microduplication in the chromosome 1q22. The rearrangement involves eleven known genes and is not present in the databases of polymorphic copy number variants.

Conclusions

The rearrangement segregates with the neurological clinical features observed in our patients, suggesting that dosage imbalance of one or more genes in this genomic region may lead to the observed phenotype. The association between the microduplication and the inflammatory disease is much less evident. Additional reported patients carrying similar microduplications are needed to clarify this aspect.