In complex with TSC2, inhibits the nutrient-mediated or growth factor-stimulated phosphorylation of S6K1 and EIF4EBP1 by negatively regulating mTORC1 signaling (By similarity). Implicated as a tumor suppressor. Involved in microtubule-mediated protein transport, but this seems to be due to unregulated mTOR signaling (PubMed:16707451). Acts as a co-chaperone for HSP90AA1 facilitating HSP90AA1 chaperoning of protein clients such as kinases, TSC2 and glucocorticoid receptor NR3C1 (PubMed:29127155). Increases ATP binding to HSP90AA1 and inhibits HSP90AA1 ATPase activity (PubMed:29127155). Competes with the activating co-chaperone AHSA1 for binding to HSP90AA1, thereby providing a reciprocal regulatory mechanism for chaperoning of client proteins (By similarity). Recruits TSC2 to HSP90AA1 and stabilizes TSC2 by preventing the interaction between TSC2 and ubiquitin ligase HERC1 (By similarity). Probably forms a complex composed of chaperones HSP90 and HSP70, co-chaperones STIP1/HOP, CDC37, PPP5C, PTGES3/p23, TSC1 and client protein TSC2 (By similarity). Forms a complex composed of chaperones HSP90 and HSP70, co-chaperones CDC37, PPP5C, TSC1 and client protein TSC2, CDK4, AKT, RAF1 and NR3C1; this complex does not contain co-chaperones STIP1/HOP and PTGES3/p23 (By similarity). Forms a complex containing HSP90AA1, TSC1 and TSC2; TSC1 is required to recruit TCS2 to the complex (By similarity). Interacts (via C-terminus) with the closed form of HSP90AA1 (via the middle domain and TPR repeat-binding motif) (PubMed:29127155). Interacts with TSC2; the interaction stabilizes TSC2 and prevents TSC2 self-aggregation (By similarity). Interacts with DOCK7 (By similarity). Interacts with FBXW5 (By similarity). Interacts with TBC1D7 (By similarity). Interacts with WDR45B (By similarity). Interacts with RPAP3 and URI1 (By similarity). At steady state found in association with membranes. The putative coiled-coil domain is necessary for interaction with TSC2. Phosphorylation at Ser-502 does not affect interaction with TSC2. Conditional knockout in glia causes an increase in HSP90AA1 ATPase activity and a down-regulation of ULK1, ERBB2, ESR1 and NR3C1 protein levels in the brain.