Function: Cochaperone that stimulates HSP90 ATPase activity (By similarity). May affect a step in the endoplasmic reticulum to Golgi trafficking. induction: By heat shock and treatment with the HSP90 inhibitor 17-demethoxygeldanamycin (17AAG). similarity: Belongs to the AHA1 family. subcellular location: May transiently interact with the endoplasmic reticulum. subunit: Interacts with HSPCA/HSP90 and with the cytoplasmic tail of the vesicular stomatitis virus glycoprotein (VSV G). Interacts with GCH1. tissue specificity: Expressed in numerous tissues, including brain, heart, skeletal muscle and kidney and, at lower levels, liver and placenta.