Ca Dyshomeostasis Disrupts Neuronal and Synaptic Function in Alzheimer's Disease

Ca homeostasis is essential for multiple neuronal functions and thus, Ca dyshomeostasis can lead to widespread impairment of cellular and synaptic signaling, subsequently contributing to dementia and Alzheimer's disease (AD). While numerous studies implicate Ca mishandling in AD, the cellular basis for loss of cognitive function remains under investigation. The process of synaptic degradation and degeneration in AD is slow, and constitutes a series of maladaptive processes each contributing to a further destabilization of the Ca homeostatic machinery. Ca homeostasis involves precise maintenance of cytosolic Ca levels, despite extracellular influx via multiple synaptic Ca channels, and intracellular release via organelles such as the endoplasmic reticulum (ER) via ryanodine receptor (RyRs) and IPR, lysosomes via transient receptor potential mucolipin channel (TRPML) and two pore channel (TPC), and mitochondria via the permeability transition pore (PTP). Furthermore, functioning of these organelles relies upon regulated inter-organelle Ca handling, with aberrant signaling resulting in synaptic dysfunction, protein mishandling, oxidative stress and defective bioenergetics, among other consequences consistent with AD. With few effective treatments currently available to mitigate AD, the past few years have seen a significant increase in the study of synaptic and cellular mechanisms as drivers of AD, including Ca dyshomeostasis. Here, we detail some key findings and discuss implications for future AD treatments.