A pathogenic human Orai1 mutation unmasks STIM1-independent rapid inactivation of Orai1 channels

The role of ion channels in the regulation of dendritic cell function

Ion channels, membrane proteins that facilitate the transport of various inorganic ions across hydrophobic cellular lipid membranes, are ubiquitous in a wide variety of cell and tissue types. They are involved in establishing the cell membrane potential and play a role in various physiological activities by regulating ion concentrations within the cell. Dendritic cells (DCs) are specialised antigen-presenting cells found mainly on the surface of the body (skin and mucous membranes), in the mesenchyme of most organs, in the T-cell compartment of the spleen and in lymph nodes. DCs exert an important influence on the regulation of inflammation by activating T cells and producing cytokines. Studies have shown that ion channels expressed in DCs contribute to the regulation of the immune response, making them a key component of the immune system. This review summarises the major scientific advances in understanding the functional impact of ion channels (calcium channels, sodium channels and aquaporin) in DCs, including the regulation of inflammatory responses, antigen presentation, maturation, migration and cytokine production, to inform ongoing studies of ion channel function in DCs.

Insights into the dynamics of the Ca2+ release-activated Ca2+ channel pore-forming complex Orai1

An important calcium (Ca2+) entry pathway into the cell is the Ca2+ release-activated Ca2+ (CRAC) channel, which controls a series of downstream signaling events such as gene transcription, secretion and proliferation. It is composed of a Ca2+ sensor in the endoplasmic reticulum (ER), the stromal interaction molecule (STIM), and the Ca2+ ion channel Orai in the plasma membrane (PM). Their activation is initiated by receptor-ligand binding at the PM, which triggers a signaling cascade within the cell that ultimately causes store depletion. The decrease in ER-luminal Ca2+ is sensed by STIM1, which undergoes structural rearrangements that lead to coupling with Orai1 and its activation. In this review, we highlight the current understanding of the Orai1 pore opening mechanism. In this context, we also point out the questions that remain unanswered and how these can be addressed by the currently emerging genetic code expansion (GCE) technology. GCE enables the incorporation of non-canonical amino acids with novel properties, such as light-sensitivity, and has the potential to provide novel insights into the structure/function relationship of CRAC channels at a single amino acid level in the living cell.

ORAI Ca2+ Channels in Cancers and Therapeutic Interventions

The ORAI proteins serve as crucial pore-forming subunits of calcium-release-activated calcium (CRAC) channels, pivotal in regulating downstream calcium-related signaling pathways. Dysregulated calcium homeostasis arising from mutations and post-translational modifications in ORAI can lead to immune disorders, myopathy, cardiovascular diseases, and even cancers. Small molecules targeting ORAI present an approach for calcium signaling modulation. Moreover, emerging techniques like optogenetics and optochemistry aim to offer more precise regulation of ORAI. This review focuses on the role of ORAI in cancers, providing a concise overview of their significance in the initiation and progression of cancers. Additionally, it highlights state-of-the-art techniques for ORAI channel modulation, including advanced optical tools, potent pharmacological inhibitors, and antibodies. These novel strategies offer promising avenues for the functional regulation of ORAI in research and may inspire innovative approaches to cancer therapy targeting ORAI.