RT Journal Article SR Electronic T1 CNKSR1 serves as a scaffold to activate an EGFR phosphatase via exclusive interaction with RhoB-GTP JF Life Science Alliance JO Life Sci. Alliance FD Life Science Alliance LLC SP e202101095 DO 10.26508/lsa.202101095 VO 4 IS 9 A1 Kanako Nishiyama A1 Masashi Maekawa A1 Tomoya Nakagita A1 Jun Nakayama A1 Takeshi Kiyoi A1 Mami Chosei A1 Akari Murakami A1 Yoshiaki Kamei A1 Hiroyuki Takeda A1 Yasutsugu Takada A1 Shigeki Higashiyama YR 2021 UL https://www.life-science-alliance.org/content/4/9/e202101095.abstract AB Epidermal growth factor receptor (EGFR) and human EGFR 2 (HER2) phosphorylation drives HER2-positive breast cancer cell proliferation. Enforced activation of phosphatases for those receptors could be a therapeutic option for HER2-positive breast cancers. Here, we report that degradation of an endosomal small GTPase, RhoB, by the ubiquitin ligase complex cullin-3 (CUL3)/KCTD10 is essential for both EGFR and HER2 phosphorylation in HER2-positive breast cancer cells. Using human protein arrays produced in a wheat cell-free protein synthesis system, RhoB-GTP, and protein tyrosine phosphatase receptor type H (PTPRH) were identified as interacting proteins of connector enhancer of kinase suppressor of Ras1 (CNKSR1). Mechanistically, constitutive degradation of RhoB, which is mediated by the CUL3/KCTD10 E3 complex, enabled CNKSR1 to interact with PTPRH at the plasma membrane resulting in inactivation of EGFR phosphatase activity. Depletion of CUL3 or KCTD10 led to the accumulation of RhoB-GTP at the plasma membrane followed by its interaction with CNKSR1, which released activated PTPRH from CNKSR1. This study suggests a mechanism of PTPRH activation through the exclusive binding of RhoB-GTP to CNKSR1.