AHSA1 also designated AHA1 is a cytosolic protein and may transiently interact with the endoplasmic reticulum. AHSA1 plays a pivotal role in regulating heat shock protein 90 (HSP 90) complex, which is essential for protein folding and stabilization under stress conditions. Specifically, AHSA1 enhances HSP 90 ATPase activity, facilitating function in protein maturation and degradation pathways. Such regulation influences "ATP lid" conformational state and promotes N-terminal dimerization, crucial for HSP 90′s activity. AHSA1 predominantly resides in cytosol but can transiently associate with endoplasmic reticulum, impacting protein trafficking from endoplasmic reticulum to Golgi apparatus. Heat shock induces AHA-1 expression in various tissues, including brain, heart, skeletal muscle, and kidney, with lower levels in liver and placenta.