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An allosteric HTRA1-calpain 2 complex with restricted activation profile.

Juliana Rey1, Maike Breiden1, Vanda Lux1

  • 1Center of Medical Biotechnology, Faculty of Biology, University Duisburg-Essen, Universitaetsstrasse, 45141 Essen, Germany.

Proceedings of the National Academy of Sciences of the United States of America
|March 29, 2022
PubMed
Summary
This summary is machine-generated.

A novel reversible activation mechanism for proteases involves a complex of HTRA1 and calpain 2. This interaction enhances soluble tau proteolysis but hinders amyloid fibril degradation, posing challenges for protein quality control.

Keywords:
HTRA1allosteryamyloid fibrilsserine proteasetau

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Area of Science:

  • Biochemistry
  • Molecular Biology
  • Protease Function

Background:

  • Classic serine proteases activate irreversibly through proteolytic processing of inactive precursors.
  • Protein aggregation, such as tau amyloid fibrils, presents challenges for cellular clearance mechanisms.

Purpose of the Study:

  • To investigate an alternative, reversible protease activation mechanism.
  • To explore the role of the HTRA1 and calpain 2 complex in tau protein and fibril processing.

Main Methods:

  • Biochemical assays to study protease activity.
  • Analysis of protein complex formation between HTRA1 and calpain 2.
  • Investigating the proteolysis of soluble tau and tau amyloid fibrils.

Main Results:

  • A reversible activation mechanism involving an inactive protease (calpain 2) and HTRA1 was identified.
  • The HTRA1-calpain 2 complex selectively enhanced soluble tau proteolysis.
  • The complex failed to efficiently degrade tau amyloid fibrils, unlike free HTRA1.

Conclusions:

  • This study reveals a unique reversible protease activation pathway with implications for protein quality control.
  • The findings highlight challenges in clearing pathogenic protein aggregates and potential off-target effects of protease modulators.