@article{ba635a9f2d1a437183953289a6d4ceae,
title = " Enhanced Dendritic Actin Network Formation in Extended Lamellipodia Drives Proliferation in Growth-Challenged Rac1 P29S Melanoma Cells ",
abstract = " Actin assembly supplies the structural framework for cell morphology and migration. Beyond structure, this actin framework can also be engaged to drive biochemical signaling programs. Here, we describe how the hyperactivation of Rac1 via the P29S mutation (Rac1 P29S ) in melanoma hijacks branched actin network assembly to coordinate proliferative cues that facilitate metastasis and drug resistance. Upon growth challenge, Rac1 P29S -harboring melanoma cells massively upregulate lamellipodia formation by dendritic actin polymerization. These extended lamellipodia form a signaling microdomain that sequesters and phospho-inactivates the tumor suppressor NF2/Merlin, driving Rac1 P29S cell proliferation in growth suppressive conditions. These biochemically active lamellipodia require cell-substrate attachment but not focal adhesion assembly and drive proliferation independently of the ERK/MAPK pathway. These data suggest a critical link between cell morphology and cell signaling and reconcile the dichotomy of Rac1{\textquoteright}s regulation of both proliferation and actin assembly by revealing a mutual signaling axis wherein actin assembly drives proliferation in melanoma. The RhoGTPase Rac1 is a regulator of cell morphology and proliferation. Mohan et al. report that these functions converge in Rac1 P29S -mutant melanoma cells. Under growth challenge, Rac1 P29S cells form extended lamellipodia that sequester and phospho-inactivate NF2/Merlin, resulting in sustained cell proliferation that is advantageous for metastasis and drug tolerance.",
keywords = "NF2, Rac1, actin assembly, lamellipodia, melanoma, merlin, proliferation",
author = "Mohan, {Ashwathi S.} and Dean, {Kevin M.} and Tadamoto Isogai and Kasitinon, {Stacy Y.} and Murali, {Vasanth S.} and Philippe Roudot and Alex Groisman and Reed, {Dana K.} and Welf, {Erik S.} and Han, {Sangyoon J.} and Jungsik Noh and Gaudenz Danuser",
note = "Funding Information: We would like to thank Dr. Sean Morrison for providing guidance for in vivo experiments and for critically reading the manuscript and Dr. Duojia Pan for providing NF2 mutant and wild-type constructs. We are grateful for assistance from John Shelton and the UT Southwestern Histo Pathology Core for providing guidance and services for tissue handling and also generous access to supplies and equipment, Dr. Katherine Luby-Phelps and the Electron Microscopy Core for access to the JEM-1400 Plus transmission electron microscope (NIH 1S10OD021685-01A1), and the BioHPC team for covering the significant needs of this project in computing and storage infrastructure. We are also grateful to the Shay/Wright Lab for both resources and guidance: Dr. Andrew Ludlow for input on CRISPR/Cas9 genome editing, Crystal Cornelius for managing and sharing the pGIPZ shRNA construct library, and Krishna Luteal for his immunohistochemistry protocol. We would also like to thank Michael Abrams and the Alto Lab for guidance on CRISPR/Cas9 genome editing and Dr. Marcel Mettlen in the Schmid Lab for his immunofluorescence protocol. This work was supported by funding from the following grants: NIH F30 CA206399 (A.S.M.), NIH F32 GM117793 (K.M.D.), Human Frontier Science Program LT000954/2015 (P.R.), NIH K25 K25CA204526 (E.S.W.), Welch Foundation I-1840 (G.D.), and NIH R01 GM071868 (G.D.). A.S.M. and G.D. conceived the project and wrote the manuscript. A.S.M. made the figures and designed and performed the experiments and analysis. K.M.D. T.I. and V.S.M. performed experiments. K.M.D. provided all constructs for imaging. S.Y.K. provided intellectual and technical input for mouse studies. T.I. provided the ARPC1B knockout cell line. D.K.R. performed EM. S.J.H. performed adhesion and TFM analyses. P.R. implemented the automatic pipeline for counting proliferating cells. J.N. quantified Merlin and PAK localization and designed and performed the analysis of lamellipodia size. Silicone substrates were provided by A.G. E.S.W. provided intellectual input. All authors reviewed and provided feedback on the manuscript. The authors declare no competing interests. Funding Information: We would like to thank Dr. Sean Morrison for providing guidance for in vivo experiments and for critically reading the manuscript and Dr. Duojia Pan for providing NF2 mutant and wild-type constructs. We are grateful for assistance from John Shelton and the UT Southwestern Histo Pathology Core for providing guidance and services for tissue handling and also generous access to supplies and equipment, Dr. Katherine Luby-Phelps and the Electron Microscopy Core for access to the JEM-1400 Plus transmission electron microscope (NIH 1S10OD021685-01A1), and the BioHPC team for covering the significant needs of this project in computing and storage infrastructure. We are also grateful to the Shay/Wright Lab for both resources and guidance: Dr. Andrew Ludlow for input on CRISPR/Cas9 genome editing, Crystal Cornelius for managing and sharing the pGIPZ shRNA construct library, and Krishna Luteal for his immunohistochemistry protocol. We would also like to thank Michael Abrams and the Alto Lab for guidance on CRISPR/Cas9 genome editing and Dr. Marcel Mettlen in the Schmid Lab for his immunofluorescence protocol. This work was supported by funding from the following grants: NIH F30 CA206399 (A.S.M.), NIH F32 GM117793 (K.M.D.), Human Frontier Science Program LT000954/2015 (P.R.), NIH K25 K25CA204526 (E.S.W.), Welch Foundation I- 1840 (G.D.), and NIH R01 GM071868 (G.D.). Publisher Copyright: {\textcopyright} 2019 Elsevier Inc.",
year = "2019",
month = may,
day = "6",
doi = "10.1016/j.devcel.2019.04.007",
language = "English (US)",
volume = "49",
pages = "444--460.e9",
journal = "Developmental cell",
issn = "1534-5807",
publisher = "Cell Press",
number = "3",
}