Inhibition of cell differentiation by Galpha q in the renal epithelial cell line LLC-PK1 |
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Authors: | Sun, Lihyun Weaver, Debora J. Amsler, Kurt Weiss, Ellen R. |
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Abstract: | LLC-PK1, an epithelial cellline derived from the kidney proximal tubule, was used to study theability of the G protein -subunit, G q, to regulate celldifferentiation. A constitutively active mutant protein, qQ209L, was expressed using theLacSwitch-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 activityof two differentiation markers,Na+-dependent hexose transport andalkaline phosphatase activity. Induction of qQ209L expression also caused achange from an epithelial to a spindle-shaped morphology. The effectsof qQ209L expression on celldifferentiation were similar to those observed with12-O-tetradecanoylphorbol 13-acetate(TPA) treatment. However, protein kinase C (PKC) levels weredownregulated in TPA-treated cells but not in qQ209L-expressing cells,suggesting that the regulation of PKC byG q may be different fromregulation by TPA. Interestingly, the PKC inhibitor GF-109203X did notinhibit the effect of IPTG on the development ofNa+-dependent hexose transport in qQ209L-expressing cells. These data implicate PKC and PKC in the pathway used byG q to block the development ofNa+-dependent hexose transport inIPTG-treated cells. |
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