Regulation of rat alveolar type 2 cell proliferation in vitro involves type II cAMP-dependent protein kinase.
To elucidate the role of cAMP and different cAMP-dependent protein kinases (PKA; A-kinase) in lung cell proliferation, we investigated rat alveolar type 2 cell proliferation in relation to activation or inhibition of PKA and PKA regulatory subunits (RIIalpha and RIalpha). Both the number of proliferating type 2 cells and the level of different regulatory subunits varied during 7 days of culture. The cells exhibited a distinct peak of proliferation after 5 days of culture. This proliferation peak was preceded by a rise in RIIalpha protein level. In contrast, an inverse relationship between RIalpha and type 2 cell proliferation was noted. Activation of PKA increased type 2 cell proliferation if given at peak RIIalpha expression. Furthermore, PKA inhibitors lowered the rate of proliferation only when a high RII level was observed. An antibody against the anchoring region of RIIalpha showed cell cycle-dependent binding in contrast to antibodies against other regions, possibly related to altered binding to A-kinase anchoring protein. Following activation of PKA, relocalization of RIIalpha was confirmed by immunocytochemistry. In conclusion, it appears that activation of PKA II is important in regulation of alveolar type 2 cell proliferation.
Samuelsen
Jan T
JT
Division of Environmental Medicine, Norwegian Institute of Public Health, Oslo, Norway. jts@niom.no
Schwarze
Per E
PE
Huitfeldt
Henrik S
HS
Thrane
E Vibeke
EV
Låg
Marit
M
Refsnes
Magne
M
Skarpen
Ellen
E
Becher
Rune
R
D000818:Animals; D002453:Cell Cycle; D049109:Cell Proliferation; D002478:Cells, Cultured; D054754:Cyclic AMP-Dependent Protein Kinase RIIalpha Subunit; D054757:Cyclic AMP-Dependent Protein Kinase RIIbeta Subunit; D054746:Cyclic AMP-Dependent Protein Kinase Type II; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism*; D004789:Enzyme Activation; D007150:Immunohistochemistry; D066298:In Vitro Techniques; D008297:Male; D011650:Pulmonary Alveoli / Q000166:cytology* / Q000201:enzymology*; D051381:Rats; D011921:Rats, Inbred WKY
D054754:Cyclic AMP-Dependent Protein Kinase RIIalpha Subunit; D054757:Cyclic AMP-Dependent Protein Kinase RIIbeta Subunit; C517822:Prkar2a protein, rat; C517839:Prkar2b protein, rat; D054746:Cyclic AMP-Dependent Protein Kinase Type II; D017868:Cyclic AMP-Dependent Protein Kinases