Mechanistic Insights into How Juxtamembrane Residue Modulation Leads To LAMP2A Inactivation in Chaperone-Mediated...

Area of Science:

• Cell Biology
• Biochemistry
• Structural Biology

Background:

• Lysosome-associated membrane protein type 2A (LAMP2A) mediates chaperone-mediated autophagy (CMA), a vital pathway for cellular homeostasis.
• LAMP2A functions via oligomeric assemblies, but the molecular basis of its trimeric stability is unclear.

Purpose of the Study:

• To investigate the role of juxtamembrane histidine protonation states in LAMP2A trimeric stability.
• To compare the structural dynamics of wild-type (WT) LAMP2A with an inactive mutant in a lysosomal membrane environment.

Main Methods:

• All-atom molecular dynamics simulations (30 μs) in a lysosomal membrane environment.
• Comparative analysis of WT LAMP2A and a mutant with altered charged residues.

Main Results:

• WT LAMP2A juxtamembrane region is stabilized by charged lipid nanoclusters, maintaining proper membrane anchoring and tilt angles.
• Mutant LAMP2A buries residues due to hydrophobic mismatch, causing altered dynamics, disrupted oligomerization, and impaired CMA activity.
• Key residues stabilizing WT oligomeric state were identified, and their loss was shown to compromise trimeric assembly in the mutant.

Conclusions:

• Juxtamembrane histidine protonation and lipid interactions are critical for LAMP2A trimeric stability and CMA function.
• Disruption of these interactions impairs CMA activity, offering insights into CMA regulation mechanisms.