ATF6alpha optimizes long-term endoplasmic reticulum function to protect cells from chronic stress.

Area of Science:

• Cellular Biology
• Molecular Biology
• Stress Response

Background:

• Vertebrates possess three key proteins—PERK, IRE1alpha, and ATF6alpha—that sense endoplasmic reticulum (ER) protein-misfolding stress.
• These sensors initiate signaling cascades to enhance cellular function, but the precise protective mechanisms of the unfolded protein response (UPR) remain unclear.

Purpose of the Study:

• To elucidate the role of ATF6alpha in the unfolded protein response (UPR).
• To determine the necessity of ATF6alpha for ER protein homeostasis during stress.

Main Methods:

• Deletion of the Atf6alpha gene in mice to create Atf6alpha null animals.
• Assessment of basal ER protein chaperone expression, embryonic and postnatal development.
• Evaluation of cellular and tissue function, protein folding, secretion, and degradation under ER stress conditions.
• In vivo challenge of Atf6alpha null animals to assess organ function and survival.

Main Results:

• ATF6alpha is not essential for basal ER protein chaperone expression or normal development.
• ATF6alpha is required for optimizing protein folding, secretion, and degradation during ER stress.
• Atf6alpha null animals exhibit compromised organ function and survival upon stress challenge.
• Functional overlap exists among the three UPR sensors, yet ATF6alpha plays a distinct role.

Conclusions:

• The ATF6alpha pathway is vital for maintaining ER function, particularly under chronic stress conditions.
• This pathway facilitates recovery from acute stress and enhances tolerance to chronic stress.
• The findings suggest an evolutionary role for ATF6alpha in sustained ER homeostasis and provide a rationale for UPR pathway redundancy.