Caveolin-1 expression and caveolae biogenesis during cell transdifferentiation in lung alveolar epithelial primary cultures.
Caveolae are omega-shaped invaginations of the plasmalemma possessing a cytoplasmic membrane protein coat of caveolin. Caveolae are present in the in vivo alveolar epithelial type I (ATI) lung cell, but absent in its progenitor, the alveolar epithelial type II (ATII) cell. In primary culture ATII cells grown on a plastic substratum acquire with time an ATI-"like" phenotype. We demonstrate that freshly isolated rat ATII cells lack caveolae and expression of caveolin-1 (a critical caveolae structural protein). As the ATII cells acquire an ATI-like phenotype in primary culture caveolin-1 expression increases, with caveolin-1 signal at 192 h postseeding up to 50-fold greater than at 60 h; caveolae were morphologically evident only after 132 h. When maintaining the differentiated ATII phenotype with time, i.e., culture upon collagen with an apical interface of air, a temporal increase in caveolin-1 expression was not observed, with only very faint signals evident even at 192 h postseeding; at no time did these cultures display caveolae. In late primary ATII cultures caveolin-1 expression and caveolae biogenesis occur as a function of in vitro transformation from the ATII to the ATI-like phenotype. The results have broad implications for the in vitro study of the role of caveolae and caveolin in alveolar epithelial cell biology.
Campbell
L
L
Welsh School of Pharmacy, Cardiff University, Cardiff, CF10 3XF, United Kingdom.
Hollins
A J
AJ
Al-Eid
A
A
Newman
G R
GR
von Ruhland
C
C
Gumbleton
M
M
D000818:Animals; D051242:Caveolin 1; D022461:Caveolins; D002454:Cell Differentiation / Q000502:physiology*; D002462:Cell Membrane / Q000502:physiology / Q000648:ultrastructure*; D002478:Cells, Cultured; D004285:Dogs; D004847:Epithelial Cells / Q000166:cytology* / Q000502:physiology; D005786:Gene Expression Regulation; D006801:Humans; D008297:Male; D008565:Membrane Proteins / Q000096:biosynthesis / Q000235:genetics*; D016253:Microscopy, Immunoelectron; D011650:Pulmonary Alveoli / Q000166:cytology*; D051381:Rats; D014407:Tumor Cells, Cultured
C495540:CAV1 protein, human; C495537:Cav1 protein, rat; D051242:Caveolin 1; D022461:Caveolins; D008565:Membrane Proteins