Am. J. Respir. Cell Mol. Biol., Vol 14, No. 6, 06 1996, 538-547.
p172: An alveolar type II and Clara cell specific protein with late developmental expression and upregulation by hyperoxic lung injury
CE Girod, DH Shin, MB Hershenson, J Solway, R Dahl and YE Miller
Division of Pulmonary Sciences and Critical Care Medicine, University of Colorado Health Sciences Center, Denver 80262, USA.
The epithelium of the alveolus and distal airway meets unique requirements,
functioning as a gas exchange membrane and barrier to alveolar flooding by
vascular contents as well as to bloodstream contamination by airborne
toxins and pathogens. Gene products specifically expressed by this
epithelium, notably the surfactant apoproteins, have had important clinical
application. No cell surface antigen specific for alveolar type II and
Clara cells has been described. We report the biochemical characterization,
tissue and developmental expression, and upregulation by injury of a 172 kD
protein recognized by a monoclonal antibody, 3F9, synthesized in response
to immunization with freshly isolated rat alveolar type II cells. p172 is
expressed in a polarized fashion by the apical surface of rat alveolar type
II and Clara cells. An immunohistochemical survey of various rat tissues
and organs reveals lung specificity. p172 is first detectable in rare
epithelial cells at 19 days of gestation, a time when the fully
differentiated alveolar type II cell is identified by the first detection
of lamellar bodies. There is a dramatic increase in p172 expression just
prior to birth. Hyperoxic lung injury results in increased expression of
p172. The upregulation of p172 by hyperoxia and its cell-specific
expression suggests an important adaptive function.
