Expression of the gas-transporting proteins, Rh B glycoprotein and Rh C glycoprotein, in the murine lung.
A family of gas-transporting proteins, the Mep/Amt/Rh glycoprotein family, has been identified recently. These are integral membrane proteins, are widely expressed in sites of gas transport, and are known to transport the gaseous molecule, NH(3), and recent evidence indicates they can transport CO(2). Because the mammalian lung is a critical site for gas transport, the current studies examine the expression of the nonerythroid members of this extended family, Rh B glycoprotein (Rhbg) and Rh C glycoprotein (Rhcg), in the normal mouse lung. Real-time RT-PCR and immunoblot analysis demonstrated both Rhbg and Rhcg mRNA and protein expression, respectively. Immunohistochemistry demonstrated both Rhbg and Rhcg were expressed in bronchial and bronchiolar epithelial cells. Rhbg was expressed by Clara cells, specifically, whereas all bronchial/bronchiolar epithelial cells, with the exception of goblet cells, expressed Rhcg. Rhbg expression was basolateral, whereas Rhcg exhibited apical and intracellular immunolabel, polarized expression similar to that observed in Rhbg- and Rhcg-expressing epithelial cells in other organs. There was no detectable expression of either Rhbg or Rhcg in alveolar endothelial or epithelial cells, in pneumocytes or in vascular tissue. In vitro studies using cultured bronchial epithelial cells confirm Rhbg and Rhcg expression, demonstrate that saturable, not diffusive, transport is the primary mechanism of ammonia/methylammonia transport, and show that the saturable transport mechanism has kinetics similar to those demonstrated previously for Rhbg and Rhcg. These findings suggest Rhbg and Rhcg may contribute to bronchial epithelial cell ammonia metabolism and suggest that they do not contribute to pulmonary CO(2) transport.
Department of Anatomy, Ewha Womans University, Seoul, Republic of Korea.
Ki-Hwan
KH
Han
Kavya
K
Mekala
Venetia
V
Babida
Hye-Young
HY
Kim
Mary E
ME
Handlogten
Jill W
JW
Verlander
I David
ID
Weiner
D000641:Ammonia / Q000378:metabolism; D000818:Animals; D001980:Bronchi / Q000166:cytology; D027682:Cation Transport Proteins / Q000235:genetics / Q000378:metabolism*; D002478:Cells, Cultured; D004847:Epithelial Cells / Q000166:cytology / Q000378:metabolism; D005260:Female; D005786:Gene Expression Regulation; D006023:Glycoproteins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D007150:Immunohistochemistry; D007668:Kidney / Q000166:cytology / Q000378:metabolism; D008168:Lung / Q000166:cytology / Q000378:metabolism*; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism*; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008807:Mice, Inbred BALB C; D021381:Protein Transport; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014598:Uteroglobin / Q000378:metabolism
D027682:Cation Transport Proteins; D006023:Glycoproteins; D008562:Membrane Glycoproteins; D026901:Membrane Transport Proteins; D012333:RNA, Messenger; C486033:RhBG protein, mouse; C485880:Rhcg protein, mouse; C556389:SCGB1A1 protein, human; C556390:Scgb1a1 protein, mouse; D000641:Ammonia; D014598:Uteroglobin