The Ron receptor tyrosine kinase activates c-Abl to promote cell proliferation through tyrosine phosphorylation of PCNA in breast cancer

Abstract

Multiple growth pathways lead to enhanced proliferation in malignant cells. However, how the core machinery of DNA replication is regulated by growth signaling remains largely unclear. The sliding clamp PCNA (Proliferating Cell Nuclear Antigen) is an indispensable component of the DNA machinery responsible for replicating the genome and maintaining genomic integrity. We previously reported that epidermal growth factor receptor (EGFR) triggered tyrosine 211 (Y211) phosphorylation of PCNA, which in turn stabilized PCNA on chromatin to promote cell proliferation. Here we show that the phosphorylation can also be catalyzed by the non-receptor tyrosine kinase c-Abl. We further demonstrate that, in the absence of EGFR, signaling to PCNA can be attained through the activation of the Ron receptor tyrosine kinase and the downstream non-receptor tyrosine kinase c-Abl. We show that Ron and c-Abl form a complex, and that activation of Ron by its ligand, HGFL, stimulates c-Abl kinase activity, which in turn directly phosphorylates PCNA at Y211 and leads to an increased level of chromatin-associated PCNA. Correspondingly, HGFL-induced Ron activation resulted in Y211 phosphorylation of PCNA while silencing of c-Abl blocked this effect. We show that cAbl and Y211 phosphorylation of PCNA is an important axis downstream of Ron, which is required for cell proliferation. Treatment with a specific peptide which inhibits Y211 phosphorylation of PCNA or with the c-Abl pharmacological inhibitor imatinib suppressed HGFL-induced cell proliferation. Our findings identify the pathway of Ron-cAbl-PCNA as a mechanism of oncogene-induced cell proliferation, with potentially important implications for development of combination therapy of breast cancer.

Geminin Overexpression Promotes Imatinib Sensitive Breast Cancer: A Novel Treatment Approach for Aggressive Breast Cancers, Including a Subset of Triple Negative

“…For instance, c-Abl translocation from the cytoplasm to the nucleus in response to serum and phosphorylation of DGKα promotes the latter cytoplasmic translocation and induction of cell proliferation and transformation [47]. C-Abl nuclear translocation was associated recently with phosphorylation of PCNA and induction of cell proliferation [48], AIB1 and tumor formation [49], and c-Jun or c-Fos and promotion of cell proliferation [50], [51]. It is possible that retention of c-Abl in the nucleus and/or expression of exclusively nuclear c-Abl protein can serve as an oncogene [52] as we showed here.…”

Forging Ahead through Darkness: PCNA, Still the Principal Conductor at the Replication Fork

“…Growth factor signaling (EGF through EGFR kinase, and HGFL through c-Abl kinase) results in phosphorylation of PCNA at Tyr211, which increases its chromatin association and protects it from degradation (Wang et al, 2006; Zhao et al, 2014). Several other signaling molecules have been shown to regulate proliferation through controlling PCNA levels, including ERK8 (Groehler and Lannigan, 2010) and 14-3-3ζ (Gao et al, 2015).…”

CBP and p300 acetylate PCNA to link its degradation with nucleotide excision repair synthesis

“…Later, phosphorylation at tyrosine 211 (Tyr211) by epidermal growth factor (EGF) receptor kinase (26), and c-Abl tyrosine kinase (27) were shown to regulate PCNA stability during DNA replication (28). The association with ERK8 kinase also influenced PCNA stability by regulating the interaction with MDM2, although no evidence that ERK8 could phosphorylate PCNA, was provided (29).…”