Hsp90 activity is necessary to acquire a proper neuronal polarization

Area of Science:

• Neuroscience
• Cell Biology
• Molecular Biology

Background:

• Chaperones, particularly Heat Shock Proteins (Hsps), regulate cellular protein folding.
• Hsp90 is abundant but its role in neuronal differentiation and axonal polarity is largely unknown.
• Neuronal polarity relies on precise protein stability and degradation.

Purpose of the Study:

• To investigate the role of Hsp90 in axonal polarity and growth during neuronal differentiation.
• To determine if Hsp90 activity is essential for axon specification and elongation.

Main Methods:

• Utilized cultured hippocampal neurons, a model system for neuronal development.
• Administered 17-AAG, a specific Hsp90 inhibitor, at different time points.
• Analyzed neuronal morphology, protein expression (Akt, GSK3), kinase activity, and motor protein distribution (kinesin-1).

Main Results:

• Hsp90 inhibition disrupted neuronal polarity and axonal elongation.
• Early inhibition (0-3h) led to multiple axon formation; later inhibition slowed elongation.
• Observed decreased Akt and GSK3 expression and activity, altered kinesin-1 distribution.
• Hsp70/Hsc70 proteins showed altered localization, potentially compensating for Hsp90 inhibition.

Conclusions:

• Hsp90 activity is essential for regulating kinases and motor proteins during axon specification and elongation.
• A critical "time-window" exists for Hsp90's role in axon specification, after which it primarily impacts elongation.