Project Summary An impermeable epithelial barrier provides a critical first line of defense for organs that interface continuously with the environment, including the skin, lung, and gut. There is growing evidence that loss of epithelial barrier integrity facilitates allergen penetration, local sensitization and, ultimately, persistence of allergic disease. Elucidation of early changes in epithelial barrier structure/function (i.e. changes that precede or coincide with sensitization may uncover new therapeutic targets and provide alternative therapies to those currently directed toward suppressing inflammation. We have recently identified a phosphatidylcholine (PC) transfer protein, Stard7, as a novel component of a pathway important for maintenance of epithelial barrier integrity: disruption of the Stard7 locus in mice resulted in increased lung epithelial barrier permeability associated with increased pulmonary inflammation, Th2 cytokines, antigen specific and total IgE, mucus cell metaplasia, and airway hyperreactivity (AHR). Our subsequent preliminary studies suggested that allergen sensitization is associated with suppression of Stard7 expression and that Stard7 deficiency is linked to disruption of mitochondrial homeostasis. Importantly, Stard7 was previously reported to promote uptake of PC by mitochondria and multiple reports have linked mitochondrial dysfunction to asthma pathogenesis. These observations lead to the central hypothesis that Stard7-mediated uptake of PC plays an integral role in mitochondrial homeostasis which, in turn, is crucial for barrier function. Based on the results of preliminary studies we propose a model in which Stard7 deficiency, downstream of allergen sensitization, results in diminished uptake of PC by mitochondria, oxidative stress and, ultimately, exacerbation of the allergic response. This model will be tested by generating novel cell and mouse lines to address the question of whether Stard7 is required for mitochondrial homeostasis and maintenance of epithelial barrier function (Aim 1), if sustained expression of Stard7 following allergen sensitization is protective (Aim 2), and if the closely related PC transfer proteins, Stard2 and/or Stard10, provide important alternate pathways for import of PC into mitochondria (Aim 3).