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RILP suppresses invasion of breast cancer cells by modulating the activity of RalA through interaction with RalGDS.

ABSTRACT: RILP (Rab7-interacting lysosomal protein) is a key regulator for late endosomal/lysosomal trafficking, and probably a tumor suppressor in prostate cancer. However, the role of RILP in other cancers and the underlying mechanism for RILP in regulating the invasion of cancer cells remain to be investigated. In this study, we showed that overexpression of RILP in breast cancer cells inhibits the migration and invasion, whereas the depletion of RILP by RNAi-mediated knockdown promotes the migration and invasion. We identified RalGDS (Ral guanine nucleotide dissociation stimulator) as a novel interacting partner for RILP, and truncation analysis revealed the N-terminal region of RILP is responsible for interacting with the guanine nucleotide exchange factor (GEF) domain of RalGDS. Immunofluorescence microscopy revealed that RalGDS can be recruited to the late endosomal compartments by RILP. Further investigations indicated that the overexpression of RILP inhibits the activity of RalA, a downstream target of RalGDS. Our data suggest that RILP suppresses the invasion of breast cancer cells by interacting with RalGDS to inhibit its GEF activity for RalA.

SUBMITTER: Wang Z

PROVIDER: S-EPMC4632296 | biostudies-other | 2015

REPOSITORIES: biostudies-other

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Project description:BackgroundGolgin-97 is a tethering factor in the trans-Golgi network (TGN) and is crucial for vesicular trafficking and maintaining cell polarity. However, the significance of golgin-97 in human diseases such as cancer remains unclear.MethodsWe searched for a potential role of golgin-97 in cancers using Kaplan-Meier Plotter ( http://kmplot.com ) and Oncomine ( www.oncomine.org ) datasets. Specific functions of golgin-97 in migration and invasion were examined in golgin-97-knockdown and golgin-97-overexpressing cells. cDNA microarray, pathway analysis and qPCR were used to identify gene profiles regulated by golgin-97. The role of golgin-97 in NF-?B signaling pathway was examined by using subcellular fractionation, luciferase reporter assay, western blot analysis and immunofluorescence assay (IFA).ResultsWe found that low expression of golgin-97 correlated with poor overall survival of cancer patients and was associated with invasiveness in breast cancer cells. Golgin-97 knockdown promoted cell migration and invasion, whereas re-expression of golgin-97 restored the above phenotypes in breast cancer cells. Microarray and pathway analyses revealed that golgin-97 knockdown induced the expression of several invasion-promoting genes that were transcriptionally regulated by NF-?B p65. Mechanistically, golgin-97 knockdown significantly reduced I?B? protein levels and activated NF-?B, whereas neither I?B? levels nor NF-?B activity was changed in TGN46- or GCC185-knockdown cells. Conversely, golgin-97 overexpression suppressed NF-?B activity and restored the levels of I?B? in golgin-97-knockdown cells. Interestingly, the results of Golgi-disturbing agent treatment revealed that the loss of Golgi integrity was not involved in the NF-?B activation induced by golgin-97 knockdown. Moreover, both TGN-bound and cytosolic golgin-97 inhibited NF-?B activation, indicating that golgin-97 functions as an NF-?B suppressor regardless of its subcellular localization.ConclusionOur results collectively demonstrate a novel and suppressive role of golgin-97 in cancer invasiveness. We also provide a new avenue for exploring the relationship between the TGN, golgin-97 and NF-?B signaling in tumor progression.

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RILP suppresses invasion of breast cancer cells by modulating the activity of RalA through interaction with RalGDS.

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