Targeting hORAI1-Mediated Calcium Influx in Triple-Negative Breast Cancer: A Computational Drug Discovery Approach

Store-operated calcium entry (SOCE) is a crucial pathway that aids in restoring depleted calcium levels in the endoplasmic reticulum (ER), consequently regulating cellular calcium homeostasis. When calcium stores are low, two key proteins are activated: STIM1, which senses the calcium levels in the ER, and ORAI1, the pore-forming subunit of calcium release-activated calcium (CRAC) channels. ORAI1 is overexpressed in triple-negative breast cancer (TNBC) and regulates the transcription of genes that regulate cancer progression. The complete atomic structure of human ORAI1 (hORAI1) remains unknown, which poses a challenge for developing targeted therapies. This study modeled the closed state of hORAI1, identifying it as a potential target for disrupting calcium influx and oncogenic signaling in TNBC. A pharmacophore hypothesis derived from Mildronate analogues was utilized to screen the COCONUT database for small compounds that stabilize the closed state of hORAI1. Five promising compounds were identified: CNP0006530, CNP0006516, CNP0008628, CNP0002844, and CNP0004972. These compounds exhibited docking scores ranging from - 7.461 to - 5.393 kcal/mol and formed stable interactions with crucial residues, Glu106 and Asp110. This likely aids in stabilizing the closed conformation and inhibiting calcium influx. Molecular dynamics simulations have demonstrated the structural stability and compactness of the lead complexes. Furthermore, principal PCA/FEL analyses have validated their conformational stability within a membrane environment. These findings provide novel insights into the structural gating processes of hORAI1 and emphasize the therapeutic potential of small compounds that target its closed state to inhibit calcium-mediated carcinogenesis in TNBC.