alphaB-crystallin interacts with cytoplasmic intermediate filament bundles during mitosis

Area of Science:

• Cell Biology
• Protein Biochemistry
• Cytoskeleton Dynamics

Background:

• Small heat-shock protein alphaB-crystallin (HSPB5) interacts with intermediate filament (IF) proteins like peripherin and vimentin.
• Previous studies demonstrated temperature-dependent in vitro binding and stress-induced recruitment of alphaB-crystallin to IFs, correlating its state with IF network remodeling.

Purpose of the Study:

• To investigate the role and intracellular distribution of alphaB-crystallin during cell division (mitosis).
• To determine if alphaB-crystallin is implicated in the remodeling of intermediate filaments during mitosis in different cell types.

Main Methods:

• Investigated intracellular distribution of alphaB-crystallin in mitotic NIH 3T3, N2a, and N1E115 cells.
• Utilized subcellular fractionation to determine alphaB-crystallin localization during mitosis.
• Analyzed alphaB-crystallin mRNA and protein levels in mitotic cells.
• Observed IF rearrangements and alphaB-crystallin recruitment in neuroblastoma cells.

Main Results:

• In NIH 3T3 cells, alphaB-crystallin remained cytosolic and diffused throughout the cell cycle, but accumulated in mitotically arrested cells due to increased mRNA levels.
• In neuroblastoma cells, IFs rearranged into cable-like structures, with alphaB-crystallin recruited onto them.
• Mitotic arrest in N2a cells led to a small fraction of alphaB-crystallin shifting to the insoluble cellular fraction.

Conclusions:

• AlphaB-crystallin's behavior during mitosis depends on the state of the intermediate filament network.
• It is either recruited to rearranged IFs or its expression is upregulated in the cytosol during cell division.