Figure 4.

Ca²⁺ homeostasis in neurons. The entrance of extracellular Ca²⁺ into neurons is due to the direct activation of neurotransmitter and neurotrophin receptors (such as NMDAR and TRK) and cationic channels (such as TRPs or voltage activated Ca²⁺ channels). The VDAC channel can import or export Ca²⁺ in the mitochondria when associated to MCU or NCLX, respectively. IP3R and VDAC channels found in MAMs can also transport Ca²⁺ from the ER to the mitochondria. The Ca²⁺ extrusion to the extracellular medium is mediated by ATPases (i.e., PMCA).