Phosphorylation of RAB7 by TBK1/IKKϵ Regulates Innate Immune Signaling in Triple-Negative Breast Cancer
Abstract
Triple-negative breast cancer (TNBC) is a heterogeneous disease enriched for mutations in PTEN and dysregulation of innate immune signaling. Here, we demonstrate that Rab7, a recently identified substrate of PTEN phosphatase activity, is also a substrate of the innate immune signaling kinases TANK-binding kinase 1 (TBK1)/IκB kinase ϵ (IKKϵ) on the same serine-72 (S72) site. An unbiased search for novel TBK1/IKKϵ substrates using stable isotope labeling with amino acids in cell culture phosphoproteomic analysis identified Rab7-S72 as a top hit. PTEN-null TNBC cells expressing a phosphomimetic version of Rab7-S72 exhibited diffuse cytosolic Rab7 localization and enhanced innate immune signaling, in contrast to a kinase-resistant version, which localized to active puncta that promote lysosomal-mediated stimulator of interferon genes (STING) degradation. Thus, convergence of PTEN loss and TBK1/IKKϵ activation on Rab7-S72 phosphorylation limited STING turnover and increased downstream production of IRF3 targets including CXCL10, CCL5, and IFNβ. Consistent with this data, PTEN-null TNBC tumors expressed higher levels of STING, and PTEN-null TNBC cell lines were hyperresponsive to STING agonists. Together, these findings begin to uncover how innate immune signaling is dysregulated downstream of TBK1/IKKϵ in a subset of TNBCs and reveals previously unrecognized cross-talk with STING recycling that may have implications for STING agonism in the clinic.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- Jan 01, 2020
- Source ID
- 10.1158/0008-5472.can-19-1310
Entities
People
- Brandon P. Piel
- David A. Barbie
- Erik H. Knelson
- Jacob D Jaffe
- Jessica L. Ritter
- Navin R. Mahadevan
- Philipp Mertins
- Saemi Han
- Steven A Carr
- Thanh U. Barbie
- Tran C. Thai
- Zehua Zhu
Organizations
- Brigham and Women's Hospital
- Dana–Farber Cancer Institute
- Helmholtz Association of German Research Centres
- National Cancer Institute
- National Institutes of Health
- United States Department of Defense