406 Modulation of Calcium Channel Activity in Darier’s Disease Keratinocytes Improves Disease Phenotypes

Darier’s disease (DD) is an autosomal dominant skin disorder characterized by acantholysis and dyskeratosis associated with mutations in ATP2A2 encoding for the sarco/endoplasmic reticulum Ca2+-ATPase pump type 2 (SERCA2), resulting in patients being functionally haploinsufficient for SERCA2. DD keratinocytes displayed a 1.5-fold increase in Ca2+ levels above that observed in control keratinocytes. This Ca2+ imbalance negatively influenced localization of protein constituents of the cell-cell adhesive junction, the desmosome, resulting in decreased desmosome function and loss of epidermal integrity. Toward resolving the Ca2+ imbalance, DD keratinocytes and controls were treated with a pharmacological SERCA2 activator, CDN1163. CDN1163 treatment of DD cells increased border localization of desmosome components plakophilin 3 and desmoplakin 2-fold above DMSO treatment, restoring desmosome formation to the level of control keratinocytes. Desmosome uniformity along cell borders was enhanced 2.5-fold above DMSO treated DD cells and 1.5-fold above DMSO treated control keratinocytes. Correspondingly, cell-cell adhesive strength was restored, evaluated by measurement of monolayer integrity upon challenge with mechanical stress. As a second approach, we utilized the compound dantrolene sodium, administered clinically as a muscle relaxant for patients with spasticity associated with CNS disorders such as multiple sclerosis, cerebral palsy and stroke. Dantrolene acts to dampen the activity of Ryanodine receptors, Ca2+ SR/ER pumps responsible for regulating Ca2+ release from ER stores. Dantrolene treatment resulted in a 2-fold increase in desmosome protein localization at DD cell borders and the restoration of monolayer integrity upon challenge with mechanical stress. These results highlight the potential for drugs designed to balance Ca2+ levels in the epidermis of DD patients as promising avenues for therapeutic intervention to reduce disease severity.