Distinct roles for Rho versus Rac/Cdc42 GTPases downstream of Vav2 in regulating mammary epithelial acinar architecture.
Non-malignant mammary epithelial cells (MECs) undergo acinar morphogenesis in three-dimensional Matrigel culture, a trait that is lost upon oncogenic transformation. Rho GTPases are thought to play important roles in regulating epithelial cell-cell junctions, but their contributions to acinar morphogenesis remain unclear. Here we report that the activity of Rho GTPases is down-regulated in non-malignant MECs in three-dimensional culture with particular suppression of Rac1 and Cdc42. Inducible expression of a constitutively active form of Vav2, a Rho GTPase guanine nucleotide exchange factor activated by receptor tyrosine kinases, in three-dimensional MEC culture activated Rac1 and Cdc42; Vav2 induction from early stages of culture impaired acinar morphogenesis, and induction in preformed acini disrupted the pre-established acinar architecture and led to cellular outgrowths. Knockdown studies demonstrated that Rac1 and Cdc42 mediate the constitutively active Vav2 phenotype, whereas in contrast, RhoA knockdown intensified the Vav2-induced disruption of acini, leading to more aggressive cell outgrowth and branching morphogenesis. These results indicate that RhoA plays an antagonistic role to Rac1/Cdc42 in the control of mammary epithelial acinar morphogenesis.
Duan
Lei
L
Eppley Institute for Cancer and Allied Diseases, University of Nebraska Medical Center, Omaha, Nebraska 68198, USA. lei_duan@rush.edu
Chen
Gengsheng
G
Virmani
Sumeet
S
Ying
GuoGuang
G
Raja
Srikumar M
SM
Chung
Byung Min
BM
Rainey
Mark A
MA
Dimri
Manjari
M
Ortega-Cava
Cesar F
CF
Zhao
Xiangshan
X
Clubb
Robert J
RJ
Tu
Chun
C
Reddi
Alagarsamy L
AL
Naramura
Mayumi
M
Band
Vimla
V
Band
Hamid
H
D002461:Cell Line, Transformed; D005260:Female; D006801:Humans; D042361:Mammary Glands, Human / Q000166:cytology / Q000254:growth & development*; D009024:Morphogenesis / Q000502:physiology*; D051567:Proto-Oncogene Proteins c-vav / Q000235:genetics / Q000378:metabolism*; D020764:cdc42 GTP-Binding Protein / Q000235:genetics / Q000378:metabolism*; D020830:rac1 GTP-Binding Protein / Q000235:genetics / Q000378:metabolism*; D020742:rhoA GTP-Binding Protein / Q000235:genetics / Q000378:metabolism*
D051567:Proto-Oncogene Proteins c-vav; C107953:RAC1 protein, human; C093651:VAV2 protein, human; C066737:RHOA protein, human; D020764:cdc42 GTP-Binding Protein; D020830:rac1 GTP-Binding Protein; D020742:rhoA GTP-Binding Protein