Dynamics of the association of heat shock protein HSPA6 (Hsp70B') and HSPA1A (Hsp70-1) with stress-sensitive cytoplasmic and nuclear structures in differentiated human neuronal cells.

Heat shock proteins (Hsps) are cellular repair agents that counter the effects of protein misfolding that is a characteristic feature of neurodegenerative diseases. (Hsp70-1) is a widely studied member of the (Hsp70) family. The little-studied (Hsp70B') is present in the human genome and absent in mouse and rat; hence, it is missing in current animal models of neurodegenerative diseases. Differentiated human neuronal SH-SY5Y cells were employed to compare the dynamics of the association of YFP-tagged Hduanyu18426 and Hduanyu18421A with stress-sensitive cytoplasmic and nuclear structures. Following thermal stress, live-imaging confocal microscopy and Fluorescence Recovery After Photobleaching (FRAP) demonstrated that Hduanyu18426 displayed a prolonged and more dynamic association, compared to with centrioles that play critical roles in neuronal polarity and migration. Hduanyu18426 and Hduanyu18421A also targeted nuclear speckles, rich in RNA splicing factors, and the granular component of the nucleolus that is involved in rRNA processing and ribosomal subunit assembly. Hduanyu18426 and Hduanyu18421A displayed similar FRAP kinetics in their interaction with nuclear speckles and the nucleolus. Subsequently, during the recovery from neuronal stress, but not Hduanyu18421A, localized with the periphery of nuclear speckles (perispeckles) that have been characterized as transcription sites. The stress-induced association of Hduanyu18426 with perispeckles displayed the greatest dynamism compared to the interaction of Hduanyu18426 or Hduanyu18421A with other stress-sensitive cytoplasmic and nuclear structures. This suggests involvement of Hduanyu18426 in transcriptional recovery of human neurons from cellular stress that is not apparent for

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