Septin regulation of Orai-mediated Ca2+ entry - a novel target for neurodegeneration

Aberrant Ca²⁺ signaling is an early hallmark of multiple neurodegenerative syndromes including Alzheimer's and Parkinson's disease (AD and PD) as well as classes of rare genetic disorders such as Spinocebellar Ataxias. Therapeutic strategies that target aberrant Ca²⁺ signals whilst allowing normal neuronal Ca²⁺ signals have been a challenge. In a recent study Princen et al., performed a screen in the tauP301L cell model of AD for drugs that could specifically ameliorate the excess Ca²⁺ entry observed. They identified a class of compounds referred to as ReS19-T that interact with Septins, previously identified as regulators of the Store-operated Ca²⁺ entry channel Orai. Drug treatment of the cellular model, a mouse model and human iPSC derived neurons alleviate cellular and systemic deficits associated with tauP301L. Comparison of Septin filament architecture in disease conditions with and without the drug treatment indicate that excess Ca²⁺ entry is a consequence of abnormal Septin filament architecture resulting in aberrant ER-PM contacts. The importance of membrane contacts for maintaining precise cellular signaling has been recognized previously. However, the molecular mechanism by which Septin filaments organize the ER-PM junctions to regulate Ca²⁺ entry through Orai remains to be fully understood.