Mast cell surfaceome characterization reveals CD98 heavy chain is critical for optimal cell function.

BACKGROUND: Mast cells are involved in many distinct pathologic conditions, suggesting that they recognize and respond to various stimuli and thus require a rich repertoire of cell surface proteins. However, mast cell surface proteomes have not been comprehensively characterized. OBJECTIVE: We aimed to further characterize the mast cell surface proteome to obtain a better understanding of how mast cells function in health and disease. METHODS: We enriched for glycosylated surface proteins expressed in mouse bone marrow-derived cultured mast cells (BMCMCs) and identified them using mass spectrometry analysis. The presence of novel surface proteins in mast cells was validated by real-time quantitative PCR and flow cytometry analysis in BMCMCs and peritoneal mast cells (PMCs). We developed a clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9 (Cas9) gene editing approach to disrupt genes of interest in BMCMCs. RESULTS: The glycoprotein enrichment approach resulted in the identification of 1270 proteins in BMCMCs, 378 of which were localized to the plasma membrane. The most common protein classes among plasma membrane proteins were small GTPases, receptors, and transporters. One such cell surface protein was CD98 heavy chain (CD98hc), encoded by the Slc3a2 gene. Slc3a2 gene disruption resulted in a significant reduction in CD98hc expression, adhesion, and proliferation. CONCLUSIONS: Glycoprotein enrichment coupled with mass spectrometry can be used to identify novel surface molecules in mast cells. Moreover, CD98hc plays an important role in mast cell function.

Mast Cells in Viral, Bacterial, and Fungal Infection Immunity.

Mast cells are granule-rich immune cells that are distributed throughout the body in areas where microorganisms typically reside, such as mucosal tissues and the skin, as well as connective tissues. It is well known that mast cells have significant roles in IgE-mediated conditions, such as anaphylaxis, but, because of their location, it is also thought that mast cells act as innate immune cells against pathogens and initiate defensive immune responses. In this review, we discuss recent studies focused on mast cell interactions with flaviviruses and Candida albicans, and mast cell function in the cecal ligation and puncture model of sepsis. We selected these studies because they are clear examples of how mast cells can either promote host resistance to infection, as previously proposed, or contribute to a dysregulated host response that can increase host morbidity and mortality. Importantly, we can distill from these studies that the contribution of mast cells to infection outcomes depends in part on the infection model, including the genetic approach used to assess the influence of mast cells on host immunity, the species in which mast cells are studied, and the differential contribution of mast cell subtypes to immunity. Accordingly, we think that this review highlights the complexity of mast cell biology in the context of innate immune responses.

Thymic stromal lymphopoietin protects in a model of airway damage and inflammation via regulation of caspase-1 activity and apoptosis inhibition.

Thymic stromal lymphopoietin (TSLP), an epithelial cell-derived cytokine, exhibits both pro-inflammatory and pro-homeostatic properties depending on the context and tissues in which it is expressed. It remains unknown whether TSLP has a similar dual role in the airways, where TSLP is known to promote allergic inflammation. Here we show that TSLP receptor (TSLPR)-deficient mice (Tslpr-/-) and mice treated with anti-TSLP antibodies exhibited increased airway inflammation and morbidity rates after bleomycin-induced tissue damage. We found that signaling through TSLPR on non-hematopoietic cells was sufficient for TSLP's protective function. Consistent with this finding, we showed that TSLP reduces caspase-1 and caspase-3 activity levels in primary human bronchial epithelial cells treated with bleomycin via Bcl-xL up-regulation. These observations were recapitulated in vivo by observing that Tslpr-/- mice showed reduced Bcl-xL expression that paralleled increased lung caspase-1 and caspase-3 activity levels and IL-1ß concentrations in the bronchial-alveolar lavage fluid. Our studies reveal a novel contribution for TSLP in preventing damage-induced airway inflammation.

Variation in common lipid parameters in malaria infected patients.

The heart is remarkably resilient even in the face of heavy parasite sequestration and other vital organ dysfunction, and deaths from cardiac arrhythmias in severe malaria are rare. Malaria may prove fatal for patients with pre-existing cardiac failure due to valvular stenosis or myocardial disease. High grade fever, parasitaemia, and fluid overload can all contribute to the problem. Cardiac arrhythmias are very rarely observed in severe falciparum malaria. An attempt has been made to evaluate the risk factors for cardiovascular diseases in malaria infected patients. In the present study the levels of total cholesterol, low density lipoproteins, triglycerides were high and the levels of high density lipoproteins were low in malaria infected patients compared to controls. The markers of free radical induced injury i.e. malondialdehyde were high. The study therefore suggests the importance of assessing these markers of oxidative stress along with the other routine investigations in malaria infected patients for initiating therapy in addition to primary and secondary preventive measures to mitigate the devastating consequences hyperlipidemia in malaria infected patients leading to cardiovascular diseases.

Variation in common lipid parameters in malaria infected patients.

The heart is remarkably resilient even in the face of heavy parasite sequestration and other vital organ dysfunction, and deaths from cardiac arrhythmias in severe malaria are rare. Malaria may prove fatal for patients with pre-existing cardiac failure due to valvular stenosis or myocardial disease. High grade fever, parasitaemia, and fluid overload can all contribute to the problem. Cardiac arrhythmias are very rarely observed in severe falciparum malaria. An attempt has been made to evaluate the risk factors for cardiovascular diseases in malaria infected patients. In the present study the levels of total cholesterol, low density lipoproteins, triglycerides were high and the levels of high density lipoproteins were low in malaria infected patients compared to controls. The markers of free radical induced injury i.e. malondialdehyde were high. The study therefore suggests the importance of assessing these markers of oxidative stress along with the other routine investigations in malaria infected patients for initiating therapy in addition to primary and secondary preventive measures to mitigate the devastating consequences hyperlipidemia in malaria infected patients leading to cardiovascular diseases.