Inhibition of cell differentiation by G alpha q in the renal epithelial cell line LLC-PK1.
LLC-PK1, an epithelial cell line derived from the kidney proximal tubule, was used to study the ability of the G protein alpha-subunit, G alpha q, to regulate cell differentiation. A constitutively active mutant protein, alpha qQ209L, was expressed using the LacSwitch-inducible mammalian expression system. Induction of alpha qQ209L expression with isopropyl-beta-D-thiogalactopyranoside (IPTG) enhanced phospholipase C activity maximally by 6- to 7.5-fold. Increasing concentrations of IPTG progressively inhibited the activity of two differentiation markers, Na(+)-dependent hexose transport and alkaline phosphatase activity. Induction of alpha qQ209L expression also caused a change from an epithelial to a spindle-shaped morphology. The effects of alpha qQ209L expression on cell differentiation were similar to those observed with 12-O-tetradecanoylphorbol 13-acetate (TPA) treatment. However, protein kinase C (PKC) levels were downregulated in TPA-treated cells but not in alpha qQ209L-expressing cells, suggesting that the regulation of PKC by G alpha q may be different from regulation by TPA. Interestingly, the PKC inhibitor GF-109203X did not inhibit the effect of IPTG on the development of Na(+)-dependent hexose transport in alpha qQ209L-expressing cells. These data implicate PKC delta and PKC epsilon in the pathway used by G alpha q to block the development of Na(+)-dependent hexose transport in IPTG-treated cells.
Sun
L
L
Department of Cell Biology and Anatomy, University of North Carolina at Chapel Hill 27599, USA.
Weaver
D J
DJ
Amsler
K
K
Weiss
E R
ER
D000469:Alkaline Phosphatase / Q000037:antagonists & inhibitors / Q000378:metabolism; D000818:Animals; D001692:Biological Transport / Q000187:drug effects / Q000502:physiology; D002454:Cell Differentiation / Q000502:physiology; D004789:Enzyme Activation / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004847:Epithelial Cells / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000235:genetics / Q000502:physiology*; D006601:Hexoses / Q000378:metabolism; D007668:Kidney / Q000166:cytology / Q000378:metabolism*; D018374:LLC-PK1 Cells / Q000166:cytology; D009154:Mutation; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism; D012964:Sodium / Q000502:physiology; D013552:Swine; D010738:Type C Phospholipases / Q000378:metabolism
D004791:Enzyme Inhibitors; D006601:Hexoses; D012964:Sodium; D011493:Protein Kinase C; D000469:Alkaline Phosphatase; D010738:Type C Phospholipases; D019204:GTP-Binding Proteins