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Lauer SM, Omar MH, Golkowski MG, Kenerson HL, Lee KS, Pascual BC, Lim HC, Forbush K, Smith FD, Gordan JD, Ong SE, Yeung RS, Scott JD. Recruitment of BAG2 to DNAJ-PKAc scaffolds promotes cell survival and resistance to drug-induced apoptosis in fibrolamellar carcinoma. Cell Rep 2024; 43:113678. [PMID: 38236773 PMCID: PMC10964278 DOI: 10.1016/j.celrep.2024.113678] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2023] [Revised: 11/23/2023] [Accepted: 01/02/2024] [Indexed: 01/30/2024] Open
Abstract
The DNAJ-PKAc fusion kinase is a defining feature of fibrolamellar carcinoma (FLC). FLC tumors are notoriously resistant to standard chemotherapies, with aberrant kinase activity assumed to be a contributing factor. By combining proximity proteomics, biochemical analyses, and live-cell photoactivation microscopy, we demonstrate that DNAJ-PKAc is not constrained by A-kinase anchoring proteins. Consequently, the fusion kinase phosphorylates a unique array of substrates, including proteins involved in translation and the anti-apoptotic factor Bcl-2-associated athanogene 2 (BAG2), a co-chaperone recruited to the fusion kinase through association with Hsp70. Tissue samples from patients with FLC exhibit increased levels of BAG2 in primary and metastatic tumors. Furthermore, drug studies implicate the DNAJ-PKAc/Hsp70/BAG2 axis in potentiating chemotherapeutic resistance. We find that the Bcl-2 inhibitor navitoclax enhances sensitivity to etoposide-induced apoptosis in cells expressing DNAJ-PKAc. Thus, our work indicates BAG2 as a marker for advanced FLC and a chemotherapeutic resistance factor in DNAJ-PKAc signaling scaffolds.
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Affiliation(s)
- Sophia M Lauer
- Department of Pharmacology, University of Washington Medical Center, Seattle, WA 98195, USA
| | - Mitchell H Omar
- Department of Pharmacology, University of Washington Medical Center, Seattle, WA 98195, USA
| | - Martin G Golkowski
- Department of Pharmacology, University of Washington Medical Center, Seattle, WA 98195, USA
| | - Heidi L Kenerson
- Department of Surgery, University of Washington Medical Center, Seattle, WA 98195, USA
| | - Kyung-Soon Lee
- Department of Pharmacology, University of Washington Medical Center, Seattle, WA 98195, USA
| | - Bryan C Pascual
- Division of Hematology and Oncology, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Huat C Lim
- Division of Hematology and Oncology, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Katherine Forbush
- Department of Pharmacology, University of Washington Medical Center, Seattle, WA 98195, USA
| | - F Donelson Smith
- Department of Pharmacology, University of Washington Medical Center, Seattle, WA 98195, USA
| | - John D Gordan
- Division of Hematology and Oncology, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Shao-En Ong
- Department of Pharmacology, University of Washington Medical Center, Seattle, WA 98195, USA
| | - Raymond S Yeung
- Department of Surgery, University of Washington Medical Center, Seattle, WA 98195, USA
| | - John D Scott
- Department of Pharmacology, University of Washington Medical Center, Seattle, WA 98195, USA.
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Omar MH, Byrne DP, Shrestha S, Lakey TM, Lee KS, Lauer SM, Collins KB, Daly LA, Eyers CE, Baird GS, Ong SE, Kannan N, Eyers PA, Scott JD. Discovery of a Cushing's syndrome protein kinase A mutant that biases signaling through type I AKAPs. SCIENCE ADVANCES 2024; 10:eadl1258. [PMID: 38381834 PMCID: PMC10881042 DOI: 10.1126/sciadv.adl1258] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/29/2023] [Accepted: 01/18/2024] [Indexed: 02/23/2024]
Abstract
Adrenal Cushing's syndrome is a disease of cortisol hypersecretion often caused by mutations in protein kinase A catalytic subunit (PKAc). Using a personalized medicine screening platform, we discovered a Cushing's driver mutation, PKAc-W196G, in ~20% of patient samples analyzed. Proximity proteomics and photokinetic imaging reveal that PKAcW196G is unexpectedly distinct from other described Cushing's variants, exhibiting retained association with type I regulatory subunits (RI) and their corresponding A kinase anchoring proteins (AKAPs). Molecular dynamics simulations predict that substitution of tryptophan-196 with glycine creates a 653-cubic angstrom cleft between the catalytic core of PKAcW196G and type II regulatory subunits (RII), but only a 395-cubic angstrom cleft with RI. Endocrine measurements show that overexpression of RIα or redistribution of PKAcW196G via AKAP recruitment counteracts stress hormone overproduction. We conclude that a W196G mutation in the kinase catalytic core skews R subunit selectivity and biases AKAP association to drive Cushing's syndrome.
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Affiliation(s)
- Mitchell H. Omar
- Department of Pharmacology, University of Washington, Seattle, WA 98195, USA
| | - Dominic P. Byrne
- Department of Biochemistry, Cell and Systems Biology, University of Liverpool, Liverpool L69 7ZB, UK
| | - Safal Shrestha
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA 30602, USA
| | - Tyler M. Lakey
- Department of Pharmacology, University of Washington, Seattle, WA 98195, USA
| | - Kyung-Soon Lee
- Department of Pharmacology, University of Washington, Seattle, WA 98195, USA
| | - Sophia M. Lauer
- Department of Pharmacology, University of Washington, Seattle, WA 98195, USA
| | - Kerrie B. Collins
- Department of Pharmacology, University of Washington, Seattle, WA 98195, USA
| | - Leonard A. Daly
- Centre for Proteome Research, Department of Biochemistry, Cell and Systems Biology, University of Liverpool, Liverpool L69 7ZB, UK
| | - Claire E. Eyers
- Centre for Proteome Research, Department of Biochemistry, Cell and Systems Biology, University of Liverpool, Liverpool L69 7ZB, UK
| | - Geoffrey S. Baird
- Department of Laboratory Medicine and Pathology, University of Washington, Seattle, WA 98195, USA
| | - Shao-En Ong
- Department of Pharmacology, University of Washington, Seattle, WA 98195, USA
| | - Natarajan Kannan
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA 30602, USA
| | - Patrick A. Eyers
- Department of Biochemistry, Cell and Systems Biology, University of Liverpool, Liverpool L69 7ZB, UK
| | - John D. Scott
- Department of Pharmacology, University of Washington, Seattle, WA 98195, USA
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Lauer SM, Omar MH, Golkowski MG, Kenerson HL, Pascual BC, Forbush K, Smith FD, Gordan J, Ong SE, Yeung RS, Scott JD. Recruitment of BAG2 to DNAJ-PKAc scaffolds promotes cell survival and resistance to drug-induced apoptosis in fibrolamellar carcinoma. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.06.28.546958. [PMID: 37425703 PMCID: PMC10327129 DOI: 10.1101/2023.06.28.546958] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/11/2023]
Abstract
The DNAJ-PKAc fusion kinase is a defining feature of the adolescent liver cancer fibrolamellar carcinoma (FLC). A single lesion on chromosome 19 generates this mutant kinase by creating a fused gene encoding the chaperonin binding domain of Hsp40 (DNAJ) in frame with the catalytic core of protein kinase A (PKAc). FLC tumors are notoriously resistant to standard chemotherapies. Aberrant kinase activity is assumed to be a contributing factor. Yet recruitment of binding partners, such as the chaperone Hsp70, implies that the scaffolding function of DNAJ- PKAc may also underlie pathogenesis. By combining proximity proteomics with biochemical analyses and photoactivation live-cell imaging we demonstrate that DNAJ-PKAc is not constrained by A-kinase anchoring proteins. Consequently, the fusion kinase phosphorylates a unique array of substrates. One validated DNAJ-PKAc target is the Bcl-2 associated athanogene 2 (BAG2), a co-chaperone recruited to the fusion kinase through association with Hsp70. Immunoblot and immunohistochemical analyses of FLC patient samples correlate increased levels of BAG2 with advanced disease and metastatic recurrences. BAG2 is linked to Bcl-2, an anti-apoptotic factor that delays cell death. Pharmacological approaches tested if the DNAJ- PKAc/Hsp70/BAG2 axis contributes to chemotherapeutic resistance in AML12 DNAJ-PKAc hepatocyte cell lines using the DNA damaging agent etoposide and the Bcl-2 inhibitor navitoclax. Wildtype AML12 cells were susceptible to each drug alone and in combination. In contrast, AML12 DNAJ-PKAc cells were moderately affected by etoposide, resistant to navitoclax, but markedly susceptible to the drug combination. These studies implicate BAG2 as a biomarker for advanced FLC and a chemotherapeutic resistance factor in DNAJ-PKAc signaling scaffolds.
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Omar MH, Kihiu M, Byrne DP, Lee KS, Lakey TM, Butcher E, Eyers PA, Scott JD. Classification of Cushing's syndrome PKAc mutants based upon their ability to bind PKI. Biochem J 2023; 480:875-890. [PMID: 37306403 PMCID: PMC11136536 DOI: 10.1042/bcj20230183] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2023] [Revised: 06/02/2023] [Accepted: 06/12/2023] [Indexed: 06/13/2023]
Abstract
Cushing's syndrome is an endocrine disorder caused by excess production of the stress hormone cortisol. Precision medicine strategies have identified single allele mutations within the PRKACA gene that drive adrenal Cushing's syndrome. These mutations promote perturbations in the catalytic core of protein kinase A (PKAc) that impair autoinhibition by regulatory subunits and compartmentalization via recruitment into AKAP signaling islands. PKAcL205R is found in ∼45% of patients, whereas PKAcE31V, PKAcW196R, and L198insW and C199insV insertion mutants are less prevalent. Mass spectrometry, cellular, and biochemical data indicate that Cushing's PKAc variants fall into two categories: those that interact with the heat-stable protein kinase inhibitor PKI, and those that do not. In vitro activity measurements show that wild-type PKAc and W196R activities are strongly inhibited by PKI (IC50 < 1 nM). In contrast, PKAcL205R activity is not blocked by the inhibitor. Immunofluorescent analyses show that the PKI-binding variants wild-type PKAc, E31V, and W196R are excluded from the nucleus and protected against proteolytic processing. Thermal stability measurements reveal that upon co-incubation with PKI and metal-bound nucleotide, the W196R variant tolerates melting temperatures 10°C higher than PKAcL205. Structural modeling maps PKI-interfering mutations to a ∼20 Å diameter area at the active site of the catalytic domain that interfaces with the pseudosubstrate of PKI. Thus, Cushing's kinases are individually controlled, compartmentalized, and processed through their differential association with PKI.
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Affiliation(s)
- Mitchell H. Omar
- Department of Pharmacology, University of Washington, Seattle, WA 98195, U.S.A
| | - Maryanne Kihiu
- Department of Pharmacology, University of Washington, Seattle, WA 98195, U.S.A
| | - Dominic P. Byrne
- Department of Biochemistry, Cell and Systems Biology, University of Liverpool, Liverpool L69 7ZB, U.K
| | - Kyung-Soon Lee
- Department of Pharmacology, University of Washington, Seattle, WA 98195, U.S.A
| | - Tyler M. Lakey
- Department of Pharmacology, University of Washington, Seattle, WA 98195, U.S.A
| | - Erik Butcher
- Department of Pharmacology, University of Washington, Seattle, WA 98195, U.S.A
| | - Patrick A. Eyers
- Department of Biochemistry, Cell and Systems Biology, University of Liverpool, Liverpool L69 7ZB, U.K
| | - John D. Scott
- Department of Pharmacology, University of Washington, Seattle, WA 98195, U.S.A
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