TA protein targeting to the ER in mammals. Mammalian TA proteins are predominantly targeted to the ER by the TRC pathway. After capture by SGTA, together with the BAG6 complex (BAG6, UBL4A, and TRC35), the TA protein is passed to the TRC40 chaperone for delivery to the ER-bound receptor complex formed by WRB and CAML. BAG6 has dual functions bridging ER targeting and ubiquitination of TA proteins and can be antagonized by SGTA. Ubiquitinated TA proteins can be deubiquitinated by ER-associated UPS20/UPS33.