Ral-Arf6 crosstalk regulates Ral dependent exocyst trafficking and anchorage independent growth signalling.
Integrin dependent regulation of growth factor signalling confers anchorage dependence that is deregulated in cancers. Downstream of integrins and oncogenic Ras the small GTPase Ral is a vital mediator of adhesion dependent trafficking and signalling. This study identifies a novel regulatory crosstalk between Ral and Arf6 that controls Ral function in cells. In re-adherent mouse fibroblasts (MEFs) integrin dependent activation of RalA drives Arf6 activation. Independent of adhesion constitutively active RalA and RalB could both however activate Arf6. This is further conserved in oncogenic H-Ras containing bladder cancer T24 cells, which express anchorage independent active Ral that supports Arf6 activation. Arf6 mediates active Ral-exocyst dependent delivery of raft microdomains to the plasma membrane that supports anchorage independent growth signalling. Accordingly in T24 cells the RalB-Arf6 crosstalk is seen to preferentially regulate anchorage independent Erk signalling. Active Ral we further find uses a Ral-RalBP1-ARNO-Arf6 pathway to mediate Arf6 activation. This study hence identifies Arf6, through this regulatory crosstalk, to be a key downstream mediator of Ral isoform function along adhesion dependent pathways in normal and cancer cells.
Indian Institute of Science Education and Research, Dr. Homi Bhabha Road, Pashan, Pune 411 008, Maharashtra, India.
Archana
A
Pawar
Robert M. Berne Cardiovascular Research Center, University of Virginia, Charlottesville, VA 22908, United States.
Jeremy A
JA
Meier
Indian Institute of Science Education and Research, Dr. Homi Bhabha Road, Pashan, Pune 411 008, Maharashtra, India.
Anwesha
A
Dasgupta
Indian Institute of Science Education and Research, Dr. Homi Bhabha Road, Pashan, Pune 411 008, Maharashtra, India.
Neha
N
Diwanji
Indian Institute of Science Education and Research, Dr. Homi Bhabha Road, Pashan, Pune 411 008, Maharashtra, India.
Neha
N
Deshpande
Indian Institute of Science Education and Research, Dr. Homi Bhabha Road, Pashan, Pune 411 008, Maharashtra, India.
Kritika
K
Saxena
Indian Institute of Science Education and Research, Dr. Homi Bhabha Road, Pashan, Pune 411 008, Maharashtra, India.
Natasha
N
Buwa
Indian Institute of Science Education and Research, Dr. Homi Bhabha Road, Pashan, Pune 411 008, Maharashtra, India.
Siddhi
S
Inchanalkar
Robert M. Berne Cardiovascular Research Center, University of Virginia, Charlottesville, VA 22908, United States; Yale Cardiovascular Research Center, 300 George Street, 7th Floor, New Haven, CT 06511, United States.
Martin Alexander
MA
Schwartz
Indian Institute of Science Education and Research, Dr. Homi Bhabha Road, Pashan, Pune 411 008, Maharashtra, India. Electronic address: nagaraj@iiserpune.ac.in.
Nagaraj
N
Balasubramanian
D000089982:ADP-Ribosylation Factor 6; D020727:ADP-Ribosylation Factors / Q000378:metabolism*; D000818:Animals; D002448:Cell Adhesion; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D002471:Cell Transformation, Neoplastic / Q000378:metabolism / Q000473:pathology; D004622:Embryo, Mammalian / Q000166:cytology; D005089:Exocytosis; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D005347:Fibroblasts / Q000378:metabolism; D006801:Humans; D021962:Membrane Microdomains / Q000378:metabolism; D051379:Mice; D021381:Protein Transport; D015398:Signal Transduction; D020725:ral GTP-Binding Proteins / Q000378:metabolism*
D000089982:ADP-Ribosylation Factor 6; C483163:Ralb protein, human; D048049:Extracellular Signal-Regulated MAP Kinases; C492198:RALA protein, human; C118120:Rala protein, mouse; D020727:ADP-Ribosylation Factors; C000715348:ARF6 protein, human; C000715727:Arf6 protein, mouse; C535173:RalB protein, mouse; D020725:ral GTP-Binding Proteins
Adhesion; Anchorage independence; Arf6; Cancer; Exocyst trafficking; Ral