An acquired scaffolding function of the DNAJ-PKAc fusion contributes to oncogenic signaling in fibrolamellar carcinoma
- University of Washington Medical Center, United States
Abstract
Fibrolamellar carcinoma (FLC) is a rare liver cancer. FLCs uniquely produce DNAJ-PKAc, a chimeric enzyme consisting of a chaperonin-binding domain fused to the Ca subunit of protein kinase A. Biochemical analyses of clinical samples reveal that a unique property of this fusion enzyme is the ability to recruit heat shock protein 70 (Hsp70). This cellular chaperonin is frequently up-regulated in cancers. Gene-editing of mouse hepatocytes generated disease-relevant AML12DNAJ-PKAc cell lines. Further analyses indicate that the proto-oncogene A-kinase anchoring protein-Lbc is up-regulated in FLC and functions to cluster DNAJ-PKAc/Hsp70 sub-complexes with a RAF-MEK-ERK kinase module. Drug screening reveals Hsp70 and MEK inhibitor combinations that selectively block proliferation of AML12DNAJ-PKAc cells. Phosphoproteomic profiling demonstrates that DNAJ-PKAc biases the signaling landscape toward ERK activation and engages downstream kinase cascades. Thus, the oncogenic action of DNAJ-PKAc involves an acquired scaffolding function that permits recruitment of Hsp70 and mobilization of local ERK signaling.
Data availability
There are no restrictions to the availability of our data. Raw mass spectrometry data has been uploaded to MassIVE, an NIH supported MS data repository (MSV000083167). Data will be made publicly available.
-
An acquired scaffolding function of the DNAJ-PKAc fusion enhances oncogenesis in Fibrolamellar carcinomaMassIVE Repository, doi:10.25345/C5F01X.
Article and author information
Author details
Lorene K Langeberg
Funding
National Institute of Diabetes and Digestive and Kidney Diseases (R01DK119192)
- John D Scott
Fibrolamellar Cancer Foundation
- John D Scott
National Cancer Institute (R21CA201867)
- Kimberly J Riehle
St. Baldrick's Foundation
- Kimberly J Riehle
National Cancer Institute (R21CA177402)
- Shao-En Ong
NIH Office of the Director (S10 OD021502)
- Shao-En Ong
National Institutes of Health (2T32CA080416)
- Rigney E Turnham
National Institute of Diabetes and Digestive and Kidney Diseases (F32DK121415)
- Mitchell H Omar
Fibrolamellar Cancer Foundation
- Raymond S Yeung
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
Copyright
© 2019, Turnham et al.
This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.
Metrics
-
- 3,065
- views
-
- 346
- downloads
-
- 50
- citations
Views, downloads and citations are aggregated across all versions of this paper published by eLife.
Download links
A two-part list of links to download the article, or parts of the article, in various formats.
Downloads (link to download the article as PDF)
Open citations (links to open the citations from this article in various online reference manager services)
Cite this article (links to download the citations from this article in formats compatible with various reference manager tools)
An acquired scaffolding function of the DNAJ-PKAc fusion contributes to oncogenic signaling in fibrolamellar carcinoma
eLife 8:e44187.
https://doi.org/10.7554/eLife.44187
Further reading
-
- Biochemistry and Chemical Biology
- Cell Biology
The Sonic hedgehog (Shh) signaling pathway controls embryonic development and tissue homeostasis after birth. This requires regulated solubilization of dual-lipidated, firmly plasma membrane-associated Shh precursors from producing cells. Although it is firmly established that the resistance-nodulation-division transporter Dispatched (Disp) drives this process, it is less clear how lipidated Shh solubilization from the plasma membrane is achieved. We have previously shown that Disp promotes proteolytic solubilization of Shh from its lipidated terminal peptide anchors. This process, termed shedding, converts tightly membrane-associated hydrophobic Shh precursors into delipidated soluble proteins. We show here that Disp-mediated Shh shedding is modulated by a serum factor that we identify as high-density lipoprotein (HDL). In addition to serving as a soluble sink for free membrane cholesterol, HDLs also accept the cholesterol-modified Shh peptide from Disp. The cholesteroylated Shh peptide is necessary and sufficient for Disp-mediated transfer because artificially cholesteroylated mCherry associates with HDL in a Disp-dependent manner, whereas an N-palmitoylated Shh variant lacking C-cholesterol does not. Disp-mediated Shh transfer to HDL is completed by proteolytic processing of the palmitoylated N-terminal membrane anchor. In contrast to dual-processed soluble Shh with moderate bioactivity, HDL-associated N-processed Shh is highly bioactive. We propose that the purpose of generating different soluble forms of Shh from the dual-lipidated precursor is to tune cellular responses in a tissue-type and time-specific manner.
-
- Biochemistry and Chemical Biology
- Cell Biology
Troubleshooting is an important part of experimental research, but graduate students rarely receive formal training in this skill. In this article, we describe an initiative called Pipettes and Problem Solving that we developed to teach troubleshooting skills to graduate students at the University of Texas at Austin. An experienced researcher presents details of a hypothetical experiment that has produced unexpected results, and students have to propose new experiments that will help identify the source of the problem. We also provide slides and other resources that can be used to facilitate problem solving and teach troubleshooting skills at other institutions.
