Localized Rho GTPase activation regulates RNA dynamics and compartmentalization in tumor cell protrusions.
mRNA trafficking and local protein translation are associated with protrusive cellular domains, such as neuronal growth cones, and deregulated control of protein translation is associated with tumor malignancy. We show here that activated RhoA, but not Rac1, is enriched in pseudopodia of MSV-MDCK-INV tumor cells and that Rho, Rho kinase (ROCK), and myosin II regulate the microtubule-independent targeting of RNA to these tumor cell domains. ROCK inhibition does not affect pseudopodial actin turnover but significantly reduces the dynamics of pseudopodial RNA turnover. Gene array analysis shows that 7.3% of the total genes analyzed exhibited a greater than 1.6-fold difference between the pseudopod and cell body fractions. Of these, only 13.2% (261 genes) are enriched in pseudopodia, suggesting that only a limited number of total cellular mRNAs are enriched in tumor cell protrusions. Comparison of the tumor pseudopod mRNA cohort and a cohort of mRNAs enriched in neuronal processes identified tumor pseudopod-specific signaling networks that were defined by expression of M-Ras and the Shp2 protein phosphatase. Pseudopod expression of M-Ras and Shp2 mRNA were diminished by ROCK inhibition linking pseudopodial Rho/ROCK activation to the localized expression of specific mRNAs. Pseudopodial enrichment for mRNAs involved in protein translation and signaling suggests that local mRNA translation regulates pseudopodial expression of less stable signaling molecules as well as the cellular machinery to translate these mRNAs. Pseudopodial Rho/ROCK activation may impact on tumor cell migration and metastasis by stimulating the pseudopodial translocation of mRNAs and thereby regulating the expression of local signaling cascades.
Department of Cellular and Physiological Sciences, Life Sciences Institute, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada.
Heather C
HC
Stuart
Zongjian
Z
Jia
Anat
A
Messenberg
Bharat
B
Joshi
T Michael
TM
Underhill
Hakima
H
Moukhles
Ivan R
IR
Nabi
D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology; D002460:Cell Line; D004285:Dogs; D004789:Enzyme Activation; D031541:Fluorescence Resonance Energy Transfer; D024462:Myosin Type II / Q000378:metabolism*; D009369:Neoplasms / Q000378:metabolism*; D015739:Nocodazole / Q000494:pharmacology; D020411:Oligonucleotide Array Sequence Analysis; D012313:RNA / Q000737:chemistry*; D012333:RNA, Messenger / Q000378:metabolism; D015398:Signal Transduction; D020741:rho GTP-Binding Proteins / Q000378:metabolism*; D054460:rho-Associated Kinases / Q000378:metabolism*
D000970:Antineoplastic Agents; D012333:RNA, Messenger; D012313:RNA; D054460:rho-Associated Kinases; D024462:Myosin Type II; D020741:rho GTP-Binding Proteins; D015739:Nocodazole