Department of Cell Biology, The Scripps Research Institute, La Jolla, CA 92037, USA.
Mol Biol Cell. 2010 Mar 15;21(6):871-84. doi: 10.1091/mbc.e09-12-1017. Epub 2010 Jan 20.
The activator of Hsp90 ATPase 1, Aha1, has been shown to participate in the Hsp90 chaperone cycle by stimulating the low intrinsic ATPase activity of Hsp90. To elucidate the structural basis for ATPase stimulation of human Hsp90 by human Aha1, we have developed novel mass spectrometry approaches that demonstrate that the N- and C-terminal domains of Aha1 cooperatively bind across the dimer interface of Hsp90 to modulate the ATP hydrolysis cycle and client activity in vivo. Mutations in both the N- and C-terminal domains of Aha1 impair its ability to bind Hsp90 and stimulate its ATPase activity in vitro and impair in vivo the ability of the Hsp90 system to modulate the folding and trafficking of wild-type and variant (DeltaF508) cystic fibrosis transmembrane conductance regulator (CFTR) responsible for the inherited disease cystic fibrosis (CF). We now propose a general model for the role of Aha1 in the Hsp90 ATPase cycle in proteostasis whereby Aha1 regulates the dwell time of Hsp90 with client. We suggest that Aha1 activity integrates chaperone function with client folding energetics by modulating ATPase sensitive N-terminal dimer structural transitions, thereby protecting transient folding intermediates in vivo that could contribute to protein misfolding systems disorders such as CF when destabilized.
Hsp90 ATPase 1 的激活剂 Aha1 被证明通过刺激 Hsp90 的低内在 ATPase 活性参与 Hsp90 伴侣循环。为了阐明 Aha1 对人 Hsp90 的 ATPase 刺激的结构基础，我们开发了新的质谱方法，证明 Aha1 的 N 端和 C 端结构域协同结合 Hsp90 的二聚体界面，以调节 ATP 水解循环和体内的客户活性。Aha1 的 N 端和 C 端结构域中的突变均损害其与 Hsp90 结合的能力，并在体外抑制其 ATPase 活性，在体内损害 Hsp90 系统调节野生型和变体（DeltaF508）囊性纤维化跨膜电导调节剂（CFTR）折叠和运输的能力，CFTR 负责遗传性疾病囊性纤维化（CF）。我们现在提出了 Aha1 在蛋白质稳态中的 Hsp90 ATPase 循环中的一般作用模型，其中 Aha1 调节 Hsp90 与客户的停留时间。我们认为，Aha1 通过调节 ATPase 敏感的 N 端二聚体结构转变来整合伴侣功能和客户折叠能量，从而保护体内的瞬时折叠中间体，这些中间体在不稳定时可能会导致蛋白质错误折叠系统疾病，如 CF。
