Naturally occurring ACE2 stalk variants are differentially released from the cell.

Area of Science:

• Biochemistry
• Molecular Biology
• Physiology

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.
• Ectodomain shedding, mediated by ADAM10 and ADAM17, releases soluble ACE2, 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 mutations affecting ACE2 release and surface expression.
• To understand how 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.

Main Results:

• Most ACE2 stalk variants showed reduced release; P734L and G726R mutations significantly increased release.
• The ACE2_P734L mutation led to higher surface expression of both ACE2 and B0AT1.
• Complex formation between ACE2 and B0AT1 did not impede ACE2 shedding by sheddases.

Conclusions:

• The ACE2 stalk region is a key determinant of ectodomain shedding efficiency.
• Naturally occurring ACE2 variants can alter soluble ACE2 release, potentially contributing to interindividual pathophysiological differences.
• Shedding regulation is independent of ACE2-B0AT1 complex stability.