CISD2 counteracts the inhibition of ER-mitochondrial calcium transfer by anti-apoptotic BCL-2.

CISD2, a 2Fe2S cluster domain-containing protein, is implicated in Wolfram syndrome type 2, longevity and cancer. CISD2 is part of a ternary complex with IP receptors (IPRs) and anti-apoptotic BCL-2 proteins and enhances BCL-2's anti-autophagic function. Here, we examined how CISD2 impacted the function of BCL-2 in apoptosis and in controlling IPR-mediated Ca signaling.

A deep phenotyping study in mouse and iPSC models to understand the role of oligodendroglia in optic neuropathy in Wolfram syndrome.

Wolfram syndrome (WS) is a rare childhood disease characterized by diabetes mellitus, diabetes insipidus, blindness, deafness, neurodegeneration and eventually early death, due to autosomal recessive mutations in the WFS1 (and WFS2) gene. While it is categorized as a neurodegenerative disease, it is increasingly becoming clear that other cell types besides neurons may be affected and contribute to the pathogenesis. MRI studies in patients and phenotyping studies in WS rodent models indicate white matter/myelin loss, implicating a role for oligodendroglia in WS-associated neurodegeneration.

ER calcium depletion as a key driver for impaired ER-to-mitochondria calcium transfer and mitochondrial dysfunction in Wolfram syndrome.

Wolfram syndrome is a rare genetic disease caused by mutations in the WFS1 or CISD2 gene. A primary defect in Wolfram syndrome involves poor ER Ca handling, but how this disturbance leads to the disease is not known. The current study, performed in primary neurons, the most affected and disease-relevant cells, involving both Wolfram syndrome genes, explains how the disturbed ER Ca handling compromises mitochondrial function and affects neuronal health.

Loss of INPP5K attenuates IP-induced Ca responses in the glioblastoma cell line U-251 MG cells.

INPP5K (inositol polyphosphate 5-phosphatase K) is an endoplasmic reticulum (ER)-resident enzyme that acts as a phosphoinositide (PI) 5-phosphatase, capable of dephosphorylating various PIs including PI 4,5-bisphosphate (PI(4,5)P), a key phosphoinositide found in the plasma membrane. Given its ER localization and substrate specificity, INPP5K may play a role in ER-plasma membrane contact sites. Furthermore, PI(4,5)P serves as a substrate for phospholipase C, an enzyme activated downstream of extracellular agonists acting on Gq-coupled receptors or tyrosine-kinase receptors, leading to IP production and subsequent release of Ca from the ER, the primary intracellular Ca storage organelle.

The ER-mitochondria interface, where Ca and cell death meet.

Endoplasmic reticulum (ER)-mitochondria contact sites are crucial to allow Ca flux between them and a plethora of proteins participate in tethering both organelles together. Inositol 1,4,5-trisphosphate receptors (IPRs) play a pivotal role at such contact sites, participating in both ER-mitochondria tethering and as Ca-transport system that delivers Ca from the ER towards mitochondria. At the ER-mitochondria contact sites, the IPRs function as a multi-protein complex linked to the voltage-dependent anion channel 1 (VDAC1) in the outer mitochondrial membrane, via the chaperone glucose-regulated protein 75 (GRP75).