ADRP in the lung: a reassessment

The PAT proteins (perilipin, ADRP, and TIP‐47) are a family of proteins that coat intracellular neutral lipid droplets. ADRP mRNA is strongly expressed in lung lipofibroblasts, and we speculated previously that ADRP may play a role in lipid transfer from lipofibroblasts to type II epithelial cells (C. J. Schultz et al., 2002 Am J Physiol Lung Cell Mol Physiol 283:L288‐L296). The type II cells need fatty acids to produce surfactant phospholipids. More recent studies reveal that isolated lipid droplets are contaminated with endogenous lipase(s). Thus, liberated fatty acids are likely taken up by the type II cells without any involvement of ADRP in the lipid transfer. ADRP is apparently involved only in the packaging and storage of triglycerides in the lipofibroblasts. Data from both tissue culture and confocal microscopy experiments will be presented to support these conclusions. The human lung carcinoma cell line, A549, was used as a model for type II cells, and neutral lipid droplets were obtained from CHO cells. Supported by the NIDDK intramural program.