Vol. 274, Issue 4, C1030-C1039, April 1998
Inhibition of cell differentiation by
G
q in the renal epithelial
cell line LLC-PK1
Lihyun
Sun1,
Debora J.
Weaver2,
Kurt
Amsler3, and
Ellen R.
Weiss1
1 Department of Cell Biology
and Anatomy, The University of North Carolina at Chapel Hill,
Chapel Hill 27599; 2 Department of
Biological Sciences, Campbell University, Buies Creek, North
Carolina 27506; and 3 Department
of Physiology and Biophysics, University of Medicine and Dentistry
of New Jersey-Robert Wood Johnson Medical School, Piscataway, New
Jersey 08854
LLC-PK1, an epithelial cell
line derived from the kidney proximal tubule, was used to study the
ability of the G protein 
-subunit, Gq, to regulate cell
differentiation. A constitutively active mutant protein,
qQ209L, was expressed using the
LacSwitch-inducible mammalian expression system. Induction of
qQ209L expression with isopropyl-
-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
qQ209L expression also caused a
change from an epithelial to a spindle-shaped morphology. The effects
of 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
qQ209L-expressing cells,
suggesting that the regulation of PKC by
Gq 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
qQ209L-expressing cells. These data implicate PKC
and PKC
in the pathway used by
Gq to block the development of
Na+-dependent hexose transport in
IPTG-treated cells.
phospholipase C; kidney; proximal tubule; protein kinase C; G
protein
