Activation-dependent substrate recruitment by the eukaryotic translation initiation factor 2 kinase PERK

Area of Science:

• Molecular Biology
• Cellular Biology
• Biochemistry

Background:

• The endoplasmic reticulum (ER) stress response involves regulated protein synthesis.
• Protein kinase R (PKR)-like ER kinase (PERK) phosphorylates eukaryotic translation initiation factor 2 alpha (eIF2alpha) to modulate protein synthesis.
• PERK activation by ER stress involves transautophosphorylation within its kinase insert loop.

Purpose of the Study:

• To elucidate the mechanism by which PERK activation enhances its affinity for eIF2alpha.
• To investigate the role of the PERK kinase insert loop in substrate binding and phosphorylation.
• To understand the conformational changes in PERK upon activation.

Main Methods:

• Protease sensitivity assays to detect conformational changes.
• In vitro binding assays to assess PERK-eIF2 complex affinity.
• In vivo phosphorylation studies of eIF2alpha.

Main Results:

• PERK activation selectively enhances its affinity for nonphosphorylated eIF2 complex.
• A significant conformational change in the PERK kinase domain occurs upon activation, indicated by altered protease sensitivity.
• The PERK kinase insert loop is essential for eIF2alpha binding and phosphorylation in vivo, despite being dispensable for catalytic activity.

Conclusions:

• Activated PERK undergoes a conformational change that enhances eIF2alpha binding.
• The kinase insert loop plays a crucial role in substrate recruitment and unidirectional phosphorylation.
• This mechanism provides novel insights into eIF2alpha regulation during ER stress.