A Study on the Role of CK2A1 in MAM Ca2+ Dynamics in Relation to DEE-66: Insights from a Genome-wide Kinase-MAM Interactome Screening

Abstract

Mitochondria-associated ER membranes (MAMs) are essential subcellular compartments that regulate multiple cellular processes, such as calcium homeostasis, lipid synthesis, and inflammation. Multiple diseases, such as neurodegenerative disorders and developmental and epileptic encephalopathy 66 (DEE-66), have been linked to the disruption or dysfunction of MAMs. My dissertation focuses on the essential function of protein kinase CK2A1 in MAM activity and its implications for the pathogenesis of DEE-66. In the first chapter, I provide a comprehensive overview of the structural composition, molecular mechanisms, emerging functions, and potential therapeutic targeting strategies of MAM. I also discuss the technical methods used to investigate MAM properties and behavior, as well as their limitations. The second chapter discusses the effect of casein kinase 2 alpha 1 (CK2A1) on the regulation of MAM composition and calcium transport, as well as its relationship with DEE-66. I identified CK2A1 as a crucial regulator of MAM composition and Ca2+ homeostasis using a genome-wide kinase-MAM interactome screening. My research indicates that phosphorylation of PACS-2 at S207/208/213 by CK2A1 facilitates MAM localization of the PACS-2-PKD2-CK2A1 complex, thereby regulating PKD2-dependent mitochondrial Ca2+ influx. In addition, I found that pathological PACS-2 mutations (E209K and E211K) associated with DEE-66 impair MAM integrity via the disruption of PACS-2 phosphorylation at S207/208/213, resulting in decreased mitochondrial Ca2+ uptake and a significant increase in cytosolic Ca2+ levels. This change in Ca2+ dynamics increases neurotransmitter release at the axon boutons of glutamatergic neurons, providing a molecular mechanism for the development of DEE-66 symptoms. In conclusion, my findings emphasize the crucial role of CK2A1 in modulating the Ca2+ dynamics of MAM and suggest a potential molecular pathway by which pathological PACS-2 mutations contribute to the onset and progression of DEE-66. Understanding the effect of CK2A1 on MAM function and its implications for DEE-66 is essential for the future development of targeted therapeutic interventions for the treatment and prevention of this neurodevelopmental disorder and other associated neurological conditions.