RAC1-Dependent ORAI1 Translocation to the Leading Edge Supports Lamellipodia Formation and Directional Persistence

Abstract

Tumor invasion requires efficient cell migration, which is achieved by the generation of persistent and polarized lamellipodia. The generation of lamellipodia is supported by actin dynamics at the leading edge where a complex of proteins known as the WAVE regulatory complex (WRC) promotes the required assembly of actin filaments to push the front of the cell ahead. By using an U2OS osteosarcoma cell line with high metastatic potential, proven by a xenotransplant in zebrafish larvae, we have studied the role of the plasma membrane Ca 2+ channel ORAI1 in this process. We have found that epidermal growth factor (EGF) triggered an enrichment of ORAI1 at the leading edge, where colocalized with cortactin (CTTN) and other members of the WRC, such as CYFIP1 and ARP2/3. ORAI1-CTTN co-precipitation was sensitive to the inhibition of the small GTPase RAC1, an upstream activator of the WRC. RAC1 potentiated ORAI1 translocation to the leading edge, increasing the availability of surface ORAI1 and increasing the plasma membrane ruffling. The role of ORAI1 at the leading edge was studied in genetically engineered U2OS cells lacking ORAI1 expression that helped us to prove the key role of this Ca 2+ channel on lamellipodia formation, lamellipodial persistence, and cell directness, which are required for tumor cell invasiveness in vivo.

The Plasma Membrane Ca2+ Pump PMCA4b Regulates Melanoma Cell Migration through Remodeling of the Actin Cytoskeleton

“…Similarly, a study reported that activation of transient receptor potential melastatin 2 (TRPM2) Ca 2+ channel by H 2 O 2 in Hela and prostate cancer (PC)-3 cells resulted in filopodia formation, loss of stress fibers, and disassembly of focal adhesion that eventually caused an increase in cell migration [ 66 ]. Another study on highly metastatic osteosarcoma cell line U2OS reported that Ca 2+ channel ORAI1 translocation to the leading edge was essential for formation of lamellipodia and cell directionality [ 67 ]. Our data are in good agreement with these findings and points to the importance of PMCA4b in mediating actin cytoskeleton rearrangement and cell motility through controlling cytosolic Ca 2+ levels.…”

Rac1, A Potential Target for Tumor Therapy

“…Actin polymerization regulated by Rac1 and Cdc42 can promote cell movement, leading to migration and invasion (19). The migration of cancer cells is closely related to the decrease of cell adhesion, rearrangement of cytoskeleton, degradation of the extracellular matrix and the formation of cell surface protrusions, which are the key factor affecting the migration of cancer cells (20). Extension of cytoplasm in the movement direction is the first step of cell movement.…”

Calcium Dynamics in Astrocytes During Cell Injury

“…MERTK can activate phospholipase C γ2 which can lead to DAG and IP3 production, thus triggering Ca 2+ release and PKC mediated Rac1 cytoskeletal rearrangement ( Todt et al, 2004 ). Additionally, a recent study demonstrated Rac1 potentiated ORAI1 translocation to the leading edge of migrating cells ( Lopez-Guerrero et al, 2020 ). The localized Ca 2+ dynamics observed in our study are likely due to cytoskeletal remodeling during astrocyte phagocytosis.…”