This study examines how high levels of vitamin D receptor (VDR) in genetic hypercalciuric stone-forming (GHS) rat tissues may cause excess calcium excretion in urine. The researchers suggest that over-expression of VDR is due to altered post-translational modification by ubiquitin and SUMO proteins, which regulate degradation of nuclear proteins like VDR. Experiments will overexpress ubiquitin and SUMO in rat tissues to analyze effects on VDR signaling and mimic the GHS phenotype. Knocking down ubiquitination enzymes will measure VDR level changes. Finally, GHS cell proteins will be isolated to check for high ubiquitin levels compared to controls. Evidence that ubiquitin/SUMO alterations affect V