Modulation of TRIM72 Alters the Repair Capacity of Lung Epithelial Cells

Abstract

The molecular mechanisms for alveolar epithelial cell plasma membrane wounding and repair are largely unknown. Previous studies identified TRIM72 (also known as mitsugumin 53) from striated muscle tissues and linked its physiological functions in these tissues to membrane repair, cell proliferation, and glucose metabolism. Here, using biochemical and immunochemical assays, we have characterized TRIM72 expression in lung tissue and cells, and investigated the physiological function of TRIM72 in the repair of alveolar epithelial cells. In vivo injury of alveolus resident cells was introduced by high tidal volume ventilation, and repair-defective cells were labeled by postinjury administration of propidium iodide and quantified in optical slices of subpleural alveoli. Primary alveolar epithelial cells were isolated to study plasma membrane wounding and repair in vitro, using a dual-dye incorporation assay following glass bead–induced damage to separately quantify injured versus repaired cells. Our results show that TRIM72 protein was expressed in alveolar epithelia of mouse, rat, and human lungs. High tidal volume ventilation of trim72 knockout mice caused significantly more fatal damage of alveolus cells as compared with the wild-type mice. Strikingly, injury estimates in trim72 overexpressor lungs were significantly lower than in the wild-type. The in vitro cell wounding assay further revealed that absence of TRIM72 led to significant repair defects in alveolar epithelial cells, whereas the total number of wounded cells (repaired plus nonrepaired) was similar in the wild-type and trim72 knockout groups. The cellular function of TRIM72 in the lung may be further linked to caveolin 1, as physical and physiological interactions were identified between these two proteins. These data suggest an important role for TRIM72 in the repair of alveolar epithelial cells under plasma membrane stress failure and potential reversal of cell repair defects by TRIM72 overexpression.