Geldanamycin induces Hsp70 and prevents α-synuclein aggregation and toxicity in vitro

Geldanamycin (GA) is a naturally occurring benzoquinone ansamycin that induces heat shock protein 70 (Hsp70). GA has been shown to reduce α-synuclein induced neurotoxicity in a fly model of Parkinson's disease. We have previously shown that heat shock proteins can prevent α-synuclein aggregation and protect against α-synuclein induced toxicity in human H4 neuroglioma cells. Here, we hypothesize that GA treatment will reduce α-synuclein aggregation and prevent α-synuclein induced toxicity and we show that GA can induce Hsp70 in a time- and concentration-dependent manner in H4 cells. Pretreatment with 200 nM GA 24 h prior to transfection prevented α-synuclein aggregation and protected against toxicity. Treatment of cells with pre-existing inclusions with GA did not result in a reduction in the number of cells containing inclusions, suggesting that upregulation of Hsp70 is not sufficient to remove established inclusions. Similarly, Western blot analysis demonstrated that GA treatment could dramatically reduce both total α-synuclein and high molecular weight α-synuclein aggregates. Taken together, these data suggest that GA is effective in preventing α-synuclein aggregation and may represent a pharmacological intervention to therapeutically increase expression of molecular chaperone proteins to treat neurodegenerative diseases where aggregation is central to the pathogenesis.