PROS1 and bronchiectasis: In view of MT functions, loss of MTs/tubulins, a cell structural protein, may be a critical basis for As-induced lung pathology such as bronchiectasis, bronchitis, COPD, etc. Synthesis of tubulin is subjected to a novel feedback autoregulation, i.e., the level of the free tubulin pool directly controls the level of tubulin expression [52].