Abstract
Chronic alterations in calcium (Ca2+) signalling in podocytes have been shown to cause proteinuria and progressive glomerular diseases. However, it is unclear whether short Ca2+ peaks influence glomerular biology and cause podocyte injury. Here we generated a DREADD (Designer Receptor Exclusively Activated by a Designer Drug) knock-in mouse line to manipulate intracellular Ca2+ levels. By mating to a podocyte-specific Cre driver we are able to investigate the impact of Ca2+ peaks on podocyte biology in living animals. Activation of the engineered G-protein coupled receptor with the synthetic compound clozapine-N-oxide (CNO) evoked a short and transient Ca2+ peak in podocytes immediately after CNO administration in vivo. Interestingly, this Ca2+ peak did neither affect glomerular perfusion nor filtration in the animals. Moreover, no obvious alterations in the glomerular morphology could be observed. Taken together, these in vivo findings suggest that chronic alterations and calcium overload rather than an induction of transient Ca2+ peaks contribute to podocyte disease.
Highlights
Diseases of the glomerular filter are a leading cause of end stage renal failure
To further study the role of Ca2+ dependent signalling events in podocytes in vivo and its implication on podocyte function we applied the DREADD (Designer Receptor Exclusively Activated by a Designer Drug) concept and generated a novel podocyte-specific transgenic mouse model in which we were able to induce increased intracellular Ca2+ levels by administration of a specific chemical compound
While the use of this retroviral gene transfer system allows expression of transgenes even in non-proliferating podocytes, which are hardly to transfect, it does not allow to control for expression levels as integration is random and can occur only once or several times
Summary
Diseases of the glomerular filter are a leading cause of end stage renal failure. Podocyte injury is the common final pathway of any glomerular disease. To further study the role of Ca2+ dependent signalling events in podocytes in vivo and its implication on podocyte function we applied the DREADD (Designer Receptor Exclusively Activated by a Designer Drug) concept and generated a novel podocyte-specific transgenic mouse model in which we were able to induce increased intracellular Ca2+ levels by administration of a specific chemical compound. To this end, we use a previously well characterized mutant human muscarinic type 3 receptor (hM3D), which leads to an exclusive activation by binding of the inert compound Clozapine-N-Oxide (CNO)[25,26]. With this in vivo approach we demonstrate that single transient Ca2+ peaks do not affect glomerular function
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