HPS6 Deficiency Leads to Reduced V-ATPase and Impaired Biogenesis of Lamellar Bodies in Alveolar Type II Cells.

Lamellar body (LB) is a tissue-specific lysosome-related organelle in type II alveolar cells, which is the main site for the synthesis, storage and secretion of pulmonary surfactants. Defects in pulmonary surfactants lead to a variety of respiratory and immune-related disorders. LB biogenesis is closely related to its function, but the underlying regulatory mechanism is largely unclear. Here, we found that deficiency of HPS6, a subunit of BLOC-2 (biogenesis of lysosome-related organelles complex-2), led to the reduction of the steady-state level of V-ATPase and the increase of luminal pH of LB. Furthermore, we observed increased LB size, accumulated surfactant proteins, and altered lipid profiling of lung tissue and bronchoalveolar lavage fluid due to HPS6 deficiency. These findings suggest that HPS6 regulates the distribution of V-ATPase on LBs to maintain its luminal acidity and LB homeostasis. This may provide new insights into the LB pathology.