ATP2B4 is an essential gene for epidermal growth factor-induced macropinocytosis in A431 cells

Area of Science:

• Cell Biology
• Molecular Biology
• Calcium Signaling

Background:

• Macropinocytosis (MPC) is a critical cellular process for fluid-phase cargo uptake.
• Stimuli-induced MPC's dependence on calcium ions (Ca²⁺) is not well understood.
• Previous studies linked constitutive MPC to extracellular Ca²⁺ sensing.

Purpose of the Study:

• To investigate the role of Ca²⁺ in epidermal growth factor (EGF)-induced MPC.
• To identify Ca²⁺-related regulators of EGF-induced MPC.
• To elucidate the mechanism by which Ca²⁺ influences MPC.

Main Methods:

• Utilized A431 human epidermoid carcinoma cells.
• Investigated mammalian homologs of coelomocyte uptake defective (CUP) genes.
• Performed ATP2B4 knockout (KO) experiments.
• Manipulated intracellular and extracellular Ca²⁺ levels.
• Assessed membrane ruffle formation, ruffle closure, and macropinosome formation.
• Analyzed Ca²⁺ oscillations.

Main Results:

• Both intracellular and extracellular Ca²⁺ are essential for EGF-induced MPC.
• ATP2B4, encoding plasma membrane Ca²⁺ ATPase 4 (PMCA4), was identified as a key regulator.
• ATP2B4 KO or Ca²⁺ depletion inhibited ruffle closure and macropinosome formation, but not ruffle formation.
• PMCA4 activity was crucial, independent of its PDZ domain-binding motif.
• ATP2B4 KO reduced EGF-stimulated Ca²⁺ oscillations during MPC.

Conclusions:

• EGF-induced MPC necessitates ATP2B4-dependent Ca²⁺ dynamics.
• PMCA4 plays a vital role in regulating Ca²⁺ homeostasis during stimulated MPC.
• Findings clarify the link between Ca²⁺ and stimuli-induced macropinocytosis.