{"doi":"10.1016/j.jbc.2022.102584","title":"Protein tyrosine kinase 6 regulates activation of SRC kinase","abstract":"Expression of Protein tyrosine kinase 6 (PTK6) is upregulated in several human solid tumors, and it has oncogenic roles in prostate and breast cancer. PTK6 and SRC kinase are distantly related, share many substrates, and often regulate the same signaling pathways, but whether they interact to regulate signaling is not well understood. We characterized crosstalk between PTK6 and SRC and show that PTK6 can directly phosphorylate SRC to promote its activation. Stable knockdown of PTK6 in multiple cancer cell lines leads to decreased activating phosphorylation of SRC. We show that coexpression of kinase-dead SRC and active PTK6 in mouse embryonic fibroblasts lacking Src, Yes, and Fyn results in activating phosphorylation of SRC. However, there is no reciprocal effect, because active SRC does not promote activating phosphorylation of PTK6. Overexpression of active PTK6 maintained activation of epidermal growth factor receptor (EGFR), AKT, and FAK, but not SHP2 and ERK1/2 in cells with knockdown of SRC. Both PTK6 and SRC are regulated by EGFR, and its inhibition with erlotinib downregulated PTK6 and to a lesser degree SRC activation in LNCaP cells that overexpress active PTK6. Erlotinib treatment also led to AKT inhibition, but overexpression of active PTK6 prevented this. Our data demonstrate overlapping and unique functions for PTK6 and SRC. Finally, we show that PTK6 and SRC are coexpressed in subsets of human prostate and breast cancer cells, and active PTK6 and active SRC colocalize in prostate cancer, supporting a role for PTK6 in promoting SRC activity in cancer. Expression of Protein tyrosine kinase 6 (PTK6) is upregulated in several human solid tumors, and it has oncogenic roles in prostate and breast cancer. PTK6 and SRC kinase are distantly related, share many substrates, and often regulate the same signaling pathways, but whether they interact to regulate signaling is not well understood. We characterized crosstalk between PTK6 and SRC and show that PTK6 can directly phosphorylate SRC to promote its activation. Stable knockdown of PTK6 in multiple cancer cell lines leads to decreased activating phosphorylation of SRC. We show that coexpression of kinase-dead SRC and active PTK6 in mouse embryonic fibroblasts lacking Src, Yes, and Fyn results in activating phosphorylation of SRC. However, there is no reciprocal effect, because active SRC does not promote activating phosphorylation of PTK6. Overexpression of active PTK6 maintained activation of epidermal growth factor receptor (EGFR), AKT, and FAK, but not SHP2 and ERK1/2 in cells with knockdown of SRC. Both PTK6 and SRC are regulated by EGFR, and its inhibition with erlotinib downregulated PTK6 and to a lesser degree SRC activation in LNCaP cells that overexpress active PTK6. Erlotinib treatment also led to AKT inhibition, but overexpression of active PTK6 prevented this. Our data demonstrate overlapping and unique functions for PTK6 and SRC. Finally, we show that PTK6 and SRC are coexpressed in subsets of human prostate and breast cancer cells, and active PTK6 and active SRC colocalize in prostate cancer, supporting a role for PTK6 in promoting SRC activity in cancer. Protein tyrosine kinase 6 (PTK6), also called BRK, is part of an intracellular family of nonreceptor tyrosine kinases, which includes FRK and SRMS, and is distantly related to the SRC family of kinases. PTK6 harbors SH domains SH3, SH2, and tyrosine kinase SH1 domains, which are required for its function, but it lacks the N-terminal SH4 domain required for myristoylation/palmitoylation and membrane targeting (1Serfas M.S. Tyner A.L. Brk, Srm, Frk, and Src42A form a distinct family of intracellular Src-like tyrosine kinases.Oncol. Res. 2003; 13: 409-419Google Scholar). This results in flexibility in intracellular localization. PTK6 is activated by auto-phosphorylation on Tyr342 and inhibited by auto-phosphorylation on Tyr447, which engages the SH2 domain in an intramolecular interaction (2Qiu H. Miller W.T. ","journal":"Journal of Biological Chemistry","year":2022,"id":265394,"datarank":0.0,"base_score":0.0,"endowment":0.0,"self_citation_contribution":0.0,"citation_network_contribution":0.0,"self_endowment_contribution":0.0,"citer_contribution":0.0,"corpus_percentile":null,"corpus_rank":null,"citation_count":11,"citer_count":0,"citers_with_citation_signal":0,"citers_with_endowment":0,"datacite_reuse_total":0,"is_dataset":false,"is_dataset_confidence":0.9564,"is_data_producer":false,"deposit_databanks":null,"is_oa":true,"file_count":0,"downloads":0,"has_version_chain":false,"published_date":"2022-01-01","fair_score":null,"fair_percentile":null,"algorithm_id":"datarank_citation_only_1hop_v6","ranking_scope":"data_only","authors":[{"id":924055,"name":"Katarina Vlajic","orcid":"0000-0002-4859-4974","position":1,"is_corresponding":false},{"id":924453,"name":"Wenjun Bie","orcid":null,"position":2,"is_corresponding":false},{"id":485029,"name":"Andre Kajdacsy‐Balla","orcid":"0000-0001-8699-762X","position":3,"is_corresponding":false},{"id":338945,"name":"Angela L. Tyner","orcid":"0000-0001-7448-8625","position":4,"is_corresponding":false},{"id":924452,"name":"Wanian M Alwanian","orcid":null,"position":0,"is_corresponding":true}],"reference_count":72,"raw_metadata":null,"created_at":"2026-07-19T00:26:45.905331Z","pmid":"36228719","pmcid":null,"fwci":null,"citation_percentile":null,"influential_citations":0,"oa_status":null,"license":null,"views":0,"total_file_size_bytes":0,"version_count":0,"fair_f":null,"fair_a":null,"fair_i":null,"fair_r":null,"fair_zscore":null,"fair_rationale":null,"fair_model":null,"fair_agent_version":null,"fair_fulltext_source":null,"fair_has_llm":null,"fair_computed_at":null,"clinical_trials":[],"software_tools":[],"db_accessions":[],"linked_datasets":[],"topics":[]}