CARMIL1-AA selectively inhibits macropinocytosis while sparing autophagy

Area of Science:

• Cell Biology
• Cancer Research
• Molecular Biology

Background:

• Macropinocytosis fuels tumor growth and drug resistance by enabling cancer cells to internalize extracellular macromolecules.
• Selective inhibition of macropinocytosis is crucial for understanding its precise role in cancer.
• The widely used inhibitor EIPA affects multiple Na+/H+ exchangers (NHE), leading to off-target effects on pH and proliferation.

Purpose of the Study:

• To develop a selective inhibitor of macropinocytosis.
• To evaluate the role of macropinocytosis in cancer progression independently of its inhibitors' side effects.
• To investigate the efficacy of CARMIL1-AA as a selective macropinocytosis inhibitor.

Main Methods:

• CRISPR-Cas9 gene editing to knock down CARMIL1.
• Expression of a CARMIL1-AA mutant to inhibit macropinocytosis.
• Assessing macropinocytosis, proliferation, RAC activation, and autophagy.
• Utilizing the inhibitor EIPA and NHE1 knockdown for comparison.

Main Results:

• EIPA inhibits proliferation more than macropinocytosis and triggers ATG8 conjugation (CASM).
• NHE1 loss did not block macropinocytosis and had off-target pH effects.
• CARMIL1-AA expression selectively inhibited macropinocytosis without affecting proliferation or autophagy.
• CARMIL1-AA demonstrated comparable inhibition to EIPA but without EIPA's side effects.

Conclusions:

• CARMIL1-AA is a selective inhibitor of macropinocytosis, offering a better tool than EIPA for studying cancer.
• Selective inhibition of macropinocytosis via CARMIL1-AA does not impede cell proliferation or autophagy.
• Targeting macropinocytosis with selective inhibitors like CARMIL1-AA is a promising strategy for cancer research.