Insulin-regulated actin dynamics is disrupted in a human keratinocyte model of Hailey-Hailey disease

The secretory pathway Ca²⁺-ATPase, SPCA1 (gene name ATP2C1), is a Golgi-localized calcium pump defective in the autosomal dominant cutaneous disorder known as Hailey-Hailey disease (HHD). Although clinically well characterized by suprabasal acantholysis and intertriginous blistering of the skin, the mechanistic underpinnings of the disease are still unclear. Here we use CRISPR/Cas9-mediated single- and biallelic ATP2C1 knockouts in immortalized human N/TERT keratinocytes to show that SPCA1 is required for dynamic reorganization of actin cytoskeleton in keratinocyte spreading, which is the primary mechanism driving skin reepithelialization. We identify an insulin-activated PI3K-AKT-Rac1 signaling pathway required for lamellipodia formation and keratinocyte spreading, defective in SPCA1 knockout cell lines. Our findings may explain the poor wound healing and impaired keratinocyte migration observed in HHD and may be relevant to the observed effect of insulin on wound healing, including diabetic wounds and burns, reported for nearly a century. Transgenic expression of hSPCA1 or treatment with CDN1163, a small molecule Ca²⁺-ATPase agonist, restored defective phenotypes in the HHD model, paving the way for future therapeutic approaches to treat this disorder.NEW & NOTEWORTHY Keratinocytes spread and change shape dynamically to maintain skin integrity and facilitate the rapid repair of the skin barrier after injury. Defects in these processes are characteristic of Hailey-Hailey disease (HHD), an ulcerative skin disorder caused by mutations in the Golgi Ca²⁺-ATPase SPCA1. By developing new keratinocyte HHD models, we uncover a role for SPCA1 in an insulin-activated signaling pathway that drives lamellipodia formation and keratinocyte spreading, linking Ca²⁺ regulation to actin cytoskeleton reorganization.