Structure and mechanism of the human NHE1-CHP1 complex

Area of Science:

• Biochemistry
• Structural Biology
• Cell Physiology

Background:

• Sodium/proton exchanger 1 (NHE1) is crucial for intracellular pH and volume homeostasis in mammalian cells.
• Calcineurin B-homologous protein 1 (CHP1) is essential for NHE1 maturation, surface expression, and pH regulation.
• Defects in NHE1 or CHP1 are linked to neurological disorders.

Purpose of the Study:

• To elucidate the structural mechanisms of human NHE1 function.
• To understand the role of CHP1 in NHE1 regulation.
• To visualize the binding of the inhibitor cariporide to NHE1.

Main Methods:

• Cryo-electron microscopy (cryo-EM) was used to determine the structures.
• The study focused on the human NHE1-CHP1 complex in different functional states.

Main Results:

• The human NHE1-CHP1 complex forms a symmetrical homodimer.
• NHE1 undergoes an elevator-like conformational change during ion transport.
• The binding site for cariporide was identified, explaining its inhibitory mechanism.
• CHP1 interacts differently with NHE1 conformations, suggesting a role in pH-sensitivity regulation.

Conclusions:

• The structures provide atomic insights into NHE1 transport and inhibition.
• CHP1's differential binding explains its regulatory role in NHE1 pH-sensitivity.
• These findings advance our understanding of cellular homeostasis and neurological disease mechanisms.