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The calcium-sensing receptor stimulates JNK in MDCK cells
J M Arthur1, M S Lawrence, C R Payne
1Molecular Signaling Group, University of Louisville, Louisville, Kentucky 40202, USA.
Abstract:
The calcium-sensing receptor (CaR) stimulates ERK1 in rat fibroblasts, but its effect on other MAP kinases is not known. We used a model of renal distal tubule, the MDCK cell, to determine the effects of CaR stimulation on Jun kinase (JNK) activity. Stimulation of the CaR with 5 mM Ca(2+) resulted in a time-dependent increase in JNK activity. Activation of JNK occurred preferentially with stimulation on the basal surface relative to the apical surface. Basal administration of the CaR agonist gadolinium (30 microm) also stimulated JNK activity. Pertussis toxin blocked the ability of both CaR agonists to stimulate JNK, indicating that the effect was mediated through G(ialpha) class G proteins. Finally, we used confocal microscopy to determine that the CaR was located predominantly on the basal surface. These studies demonstrate for the first time that the CaR stimulates JNK activity.
Insights
The calcium-sensing receptor (CaR) activates Jun kinase (JNK) in kidney cells. This CaR-mediated JNK activation occurs via G-alpha-i proteins and is localized to the basal cell surface.
Area of Science:
- Cell biology
- Molecular signaling
- Renal physiology
Background:
- The calcium-sensing receptor (CaR) is known to activate ERK1 in fibroblasts.
- Its effects on other mitogen-activated protein kinases (MAPKs), such as Jun kinase (JNK), remain largely uncharacterized.
- Understanding CaR signaling in renal cells is crucial for kidney function.
Purpose of the Study:
- To investigate the impact of CaR stimulation on JNK activity in a renal cell model.
- To elucidate the signaling pathways and cellular localization involved in CaR-mediated JNK activation.
Main Methods:
- Utilized Madin-Darby canine kidney (MDCK) cells as a model for the renal distal tubule.
- Stimulated CaR using calcium (Ca2+) and gadolinium.
- Assessed JNK activity through biochemical assays.
- Investigated G protein involvement using pertussis toxin.
- Determined CaR localization via confocal microscopy.
Main Results:
- CaR stimulation with 5 mM Ca2+ induced a time-dependent increase in JNK activity.
- JNK activation was more pronounced upon stimulation of the basal cell surface compared to the apical surface.
- Basal administration of the CaR agonist gadolinium also stimulated JNK.
- Pertussis toxin inhibited CaR-induced JNK activation, implicating G-alpha-i proteins.
- Confocal microscopy revealed predominant CaR localization on the basal surface of MDCK cells.
Conclusions:
- The calcium-sensing receptor (CaR) stimulates Jun kinase (JNK) activity in renal cells.
- This activation is mediated by G-alpha-i class G proteins.
- CaR-JNK signaling is preferentially initiated from the basal surface of the renal tubule cells.