Naturally occurring ACE2 stalk variants are differentially released from the cell

Area of Science:

• Biochemistry
• Molecular Biology
• Cell Biology

Background:

• Angiotensin-converting enzyme 2 (ACE2) regulates the renin-angiotensin-aldosterone system (RAAS) and serves as the SARS-CoV-2 receptor.
• ACE2 stabilizes the B0AT1 amino acid transporter, making its surface expression critical for physiological functions.
• Soluble ACE2 is generated via ectodomain shedding, primarily by ADAM10 and ADAM17, but regulatory mechanisms are not fully understood.

Purpose of the Study:

• To investigate the role of the ACE2 stalk region in ectodomain shedding.
• To identify specific single-point mutations affecting ACE2 release and surface expression.
• To determine if B0AT1 complex formation influences ACE2 shedding.

Main Methods:

• Analysis of 11 naturally occurring single-point mutations in the ACE2 stalk region.
• Quantification of soluble ACE2 release compared to wild-type (WT) ACE2.
• Assessment of surface ACE2 and B0AT1 levels.
• Investigation of ACE2 shedding in the presence of the B0AT1 complex.

Main Results:

• Most ACE2 stalk region mutations significantly reduced ectodomain shedding.
• The P734L and G726R mutations markedly increased ACE2 release.
• ACE2_P734L variant showed enhanced surface expression, leading to increased B0AT1 surface levels.
• B0AT1 complex formation did not impede ACE2 shedding by sheddases.

Conclusions:

• The ACE2 stalk region is a critical determinant of ectodomain shedding efficiency.
• Naturally occurring ACE2 variants can alter soluble ACE2 release, potentially contributing to interindividual pathophysiological differences.
• Complex formation with B0AT1 does not restrict ACE2 shedding, suggesting sheddase access is not sterically hindered.