Lysophosphatidic Acid Triggers Apoptosis in HeLa Cells through the Upregulation of Tumor Necrosis Factor Receptor Superfamily Member 21

Figure 7

DR6 induction is responsible for LPA-induced apoptosis and sketch of mechanism. (a) Overexpression of DR6 induced apoptosis. HeLa cells were transiently infected with adenoviruses encoding constitutively active DR6 with different multiplicity of infection (MOI); or a control adenovirus carrying the LacZ gene (LacZ). After 24 hr infection, cells were harvested, and the lysates were separated by SDS-PAGE, followed by Western blot analysis for DR6 expression, caspase activation, and PARP cleavage. This membrane was also reprobed with anti-β-actin antibody to indicate relative loading of samples (bottom panel). The blot is a representative of 3 independent experiments (). (b) Downregulation of DR6 expression by siRNA attenuates LPA-triggered apoptosis. HeLa cells were treated with LPA in the presence of control siRNA or DR6 siRNA. The expressions of DR6 and activation of caspase-7, caspase-3, and PARP cleavage were measured by Western analysis. . (c) The proposed molecular mechanism of LPA-induced DR6 expression in HeLa cells. LPA ligand binds to its receptors LPAR1 or LPAR3 to initiate the cell signaling by activation PI3K, followed by the activation of PKC δ and MEK, which phosphorylate ERK1/2. ERK then activates CREB probably mediated by activation of P90-RSK.

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