S-Acylation Is A Key Regulator of Orai1/Stim1-Mediated Store-Operated Calcium Entry In T Cells

<p>Orai1 and STIM1 proteins are the essential components of the Ca²⁺ release activated Ca²⁺ (CRAC) channel which is required for store-operated Ca²⁺ entry (SOCE) in T cells and subsequent signaling events leading to T cell activation, proliferation, and differentiation. Plasma membrane (PM)-localized Orai1 is the pore-forming subunit of the CRAC channel, and STIM1 is the Ca²⁺ sensor localized to the endoplasmic reticulum (ER) membrane in quiescent T cells. T cell receptor (TCR) stimulation leads to depletion of ER Ca²⁺ stores resulting in Ca²⁺ no longer being bound to STIM1. This activates STIM1 by triggering a lengthening conformational change which allows it to bind Orai1 at ER-PM junctions within the immunological synapse. Binding of STIM1 to Orai1 activates the CRAC channel resulting in SOCE. Although the functional importance of these events is well-known, the molecular mechanism supporting timely and efficient recruitment of both Orai1 and STIM1 to the ER-PM junctions remains poorly understood. We have found that, among several other TCR machinery proteins, both Orai1 and STIM1 are rapidly and transiently S-acylated upon TCR stimulation. Furthermore, using electrophysiology studies and Fura-2 Ca²⁺ imaging, we demonstrated that both Orai1 and STIM1 require S-acylation to form active CRAC channels and mediate SOCE. Lastly, our studies using total internal reflection fluorescence microscopy showed that a lack of S-acylation of either Orai1 or STIM1 resulted in significantly reduced Orai1/STIM1 colocalization as evident from the diminished PM puncta formation. These data describe a novel form of SOCE regulation in T cells that may provide new therapeutic avenues to treat diseases caused by dysfunctional CRAC channels, such as severe combined immunodeficiency and Störmorken syndrome.</p>

Name thesis:degree_name

Doctor of Philosophy (PhD)

Level thesis:degree_level

Dissertation (PhD)

Year dc:date.available

2023

Authors dc:creator

• Diaz, Savannah J. West
• <p>0000-0002-2106-7680</p>

Contributors dc:contributor

• Askar Akimzhanov, PhD
• Darren Boehning, PhD
• Ilya Levental, PhD

• S-acylation
• calcium signaling
• T cells
• palmitoylation
• DHHC enzymes
• Biochemistry, Biophysics, and Structural Biology
• Cell Biology

Repository record dc:identifier

https://digitalcommons.library.tmc.edu/utgsbs_dissertations/1242

OAI identifier oai:identifier

oai:digitalcommons.library.tmc.edu:utgsbs_dissertations-2299