Myosin IIA associates with NK cell lytic granules to enable their interaction with F-actin and function at the immunological synapse.

NK cell cytotoxicity requires the formation of an actin-rich immunological synapse (IS) with a target cell and the polarization of perforin-containing lytic granules toward the IS. Following the polarization of lytic granules, they traverse through the actin-rich IS to join the NK cell membrane in order for directed secretion of their contents to occur. We examined the role of myosin IIA as a candidate for facilitating this prefinal step in lytic NK cell IS function. Lytic granules in and derived from a human NK cell line, or ex vivo human NK cells, were constitutively associated with myosin IIA. When isolated using density gradients, myosin IIA-associated NK cell lytic granules directly bound to F-actin and the interaction was sensitive to the presence of ATP under conditions of flow. In NK cells from patients with a truncation mutation in myosin IIA, NK cell cytotoxicity, lytic granule penetration into F-actin at the IS, and interaction of isolated granules with F-actin were all decreased. Similarly, inhibition of myosin function also diminished the penetration of lytic granules into F-actin at the IS, as well as the final approach of lytic granules to and their dynamics at the IS. Thus, NK cell lytic granule-associated myosin IIA enables their interaction with actin and final transit through the actin-rich IS to the synaptic membrane, and can be defective in the context of naturally occurring human myosin IIA mutation.

Differential microRNA epression in asthma and the role of miR-1248 in regulation of IL-5.

Asthma is a chronic inflammatory disease that can be difficult to manage due to a lack of diagnostic biomarkers and an incomplete understanding of the molecular pathogenesis. MicroRNAs (miRNAs) are small, single-stranded, non-coding RNAs with increasing importance in regulation of immune function and as biomarkers. We profiled miRNAs in the serum of asthmatics and non-asthmatic controls to identify miRNAs that could serve as diagnostic markers and potential regulators of allergic inflammation. Differential expression of miR-1248, miR-26a, Let-7a, and Let-7d were observed in asthmatic patients compared to controls. Predictive algorithm analyses of these miRNAs revealed their specificity for different Th2 cytokines, including IL-5, which has not previously been shown to be post-transcriptionally regulated. Using multiple approaches, we showed that miR-1248 physically interacts with the IL-5 transcript in the 3' untranslated region and serves as a positive regulator to increase IL-5 expression. Collectively, our results demonstrate a previously uncharacterized mode of regulation of IL-5 expression and potential use for miRNAs in the diagnosis and clinical management of asthma.