Macropinocytosis of protein is an amino acid supply route in Ras-transformed cells


Macropinocytosis is a highly conserved endocytic process by which extracellular fluid and its contents are internalized into cells through large, heterogeneous vesicles known as macropinosomes. Oncogenic Ras proteins have been shown to stimulate macropinocytosis but the functional contribution of this uptake mechanism to the transformed phenotype remains unknown1,2,3. Here we show that Ras-transformed cells use macropinocytosis to transport extracellular protein into the cell. The internalized protein undergoes proteolytic degradation, yielding amino acids including glutamine that can enter central carbon metabolism. Accordingly, the dependence of Ras-transformed cells on free extracellular glutamine for growth can be suppressed by the macropinocytic uptake of protein. Consistent with macropinocytosis representing an important route of nutrient uptake in tumours, its pharmacological inhibition compromises the growth of Ras-transformed pancreatic tumour xenografts. These results identify macropinocytosis as a mechanism by which cancer cells support their unique metabolic needs and point to the possible exploitation of this process in the design of anticancer therapies.

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Figure 1: Oncogenic KRAS-expressing pancreatic cancer cells display increased levels of macropinocytosis both in culture and in vivo.
Figure 2: Oncogenic Kras-induced macropinocytosis in mouse NIH 3T3 cells mediates the internalization of extracellular albumin, which is subsequently targeted for proteolytic degradation.
Figure 3: Macropinocytic uptake of extracellular protein drives the accumulation of catabolic intermediates and entry of protein-derived amino acids into central carbon metabolism.
Figure 4: Macropinocytosis is required for albumin-dependent cancer cell proliferation in vitro and for tumour growth in vivo.

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  • 29 May 2013

    Minor changes were made to the Methods Summary in the PDF.


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We are grateful to members of the Bar-Sagi laboratory for their comments and discussions, and N. Fehrenbacher and M. Philips for sharing cell lines. This work was supported National Institutes of Health (NIH) grant R01CA055360 to D.B.-S. C.C. was supported by a Canadian Institutes of Health Research postdoctoral fellowship and an AACR postdoctoral fellowship provided by the Pancreatic Cancer Action Network. M.G.V.H. acknowledges support from the Burroughs Wellcome Fund, the Damon Runyon Cancer Research Foundation, the Smith Family, the Stern family, the Broad Institute and the National Cancer Institute (P01-CA117969 and P30-CA14051-39). J.J.K. was supported by a Hope Funds for Cancer Research Fellowship (HFCR-11-03-01). C.B.T., J.A.D. and J.D.R. acknowledge support by the Stand Up To Cancer (SU2C) Pancreatic Cancer Dream Team Award. All animal care and procedures were approved by the Institutional Animal Care and Use Committee at NYU School of Medicine. The Histopathology Core of NYU School of Medicine is partially supported by the National Institutes of Health (grant 5 P30CA016087-32). Troma I, an antibody that recognizes CK8, was contributed by P. Brulet and R. Kemler and made available by the Developmental Studies Hybridoma Bank under the auspices of the NICHD.

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C.C. and D.B.-S. conceived the cell biological and cell-growth experiments. C.C. carried out the macropinocytic assays, microscopy and proliferation assays. C.C. and R.G.S.-A. carried out the xenograft experiments. C.C. and E.G. carried out the KRAS knockdown experiments. S.M.D., S.J.P., C.M.M. and M.G.V.H. conceived and carried out the 13C-labelling experiments. J.J.K., S.H., M.N., J.A.D., C.B.T. and J.D.R. conceived and carried out the human metabolomics analysis.

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Correspondence to Dafna Bar-Sagi.

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Commisso, C., Davidson, S., Soydaner-Azeloglu, R. et al. Macropinocytosis of protein is an amino acid supply route in Ras-transformed cells. Nature 497, 633–637 (2013).

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