BAG3 and Parkinson disease: Intriguingly, STIP1 levels were elevated in all of these brain regions from PD patients, along with seven other chaperones and co-chaperones (AHSA1, DNAJB1, HSPA1A, HSPA1B, BAG3, PTGES3, HSP90AA1, Fig. 1 m, n), most of which interact with and regulate the Hsp70/90 machinery.