CYRI-B mediated macropinocytosis drives metastasis via lysophosphatidic acid receptor uptake

  1. Savvas Nikolaou
  2. Amelie Juin
  3. Jamie A. Whitelaw
  4. Nikki R. Paul
  5. Loic Fort
  6. Colin Nixon
  7. Heather J. Spence
  8. Sheila Bryson
  9. Laura M. Machesky

  • Curated by eLife

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    eLife assessment

    This important study combines in vivo and in vitro models to characterise the role of CYRI-B, an interactor of the small GTPase Rac1, in controlling pancreatic cancer progression towards a higher proliferative and metastatic stage. The evidence supporting the claims of the authors is convincing in characterizing a novel Rac1 binding protein, CYRI-B, as a regulator of metastatic potential in vivo, with distinct functions at different stages of tumour progression. CYRI-B reduces the typical hyperactivation of Rac1 in the early stages of tumour progression; subsequently, CYRI-B mediates internalization of lysophosphatidic acid receptor 1 (LPAR1) uptake through macropinocytosis, thus regulating chemotactic migration of cancer cells towards lysophosphatidic acid (LPA). Although the inclusion of human pancreatic cancer cell lines would have strengthened the study, the work will be of broad interest to cell biologists and the signalling research communities.

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Abstract

Pancreatic ductal adenocarcinoma carries a dismal prognosis, with high rates of metastasis and few treatment options. Hyperactivation of KRAS in almost all tumours drives RAC1 activation, conferring enhanced migratory and proliferative capacity as well as macropinocytosis. Macropinocytosis is well understood as a nutrient scavenging mechanism, but little is known about its functions in trafficking of signaling receptors. We find that CYRI-B is highly expressed in pancreatic tumours in a mouse model of KRAS and p53- driven pancreatic cancer. Deletion of CYRI-B accelerates tumourigenesis, leading to enhanced ERK and JNK-induced proliferation in precancerous lesions, indicating a role as a buffer of RAC1 hyperactivation in early stages. However, as disease progresses, loss of CYRI-B inhibits metastasis. CYRI-B depleted tumour cells show reduced chemotactic responses to lysophosphatidic acid, a major driver of tumour spread, due to impaired macropinocytic uptake of LPAR1 receptor. Overall, we implicate CYRI-B as a mediator of growth and signaling in pancreatic cancer, providing new insights into pathways controlling metastasis.

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  1. eLife

    eLife assessment

    This important study combines in vivo and in vitro models to characterise the role of CYRI-B, an interactor of the small GTPase Rac1, in controlling pancreatic cancer progression towards a higher proliferative and metastatic stage. The evidence supporting the claims of the authors is convincing in characterizing a novel Rac1 binding protein, CYRI-B, as a regulator of metastatic potential in vivo, with distinct functions at different stages of tumour progression. CYRI-B reduces the typical hyperactivation of Rac1 in the early stages of tumour progression; subsequently, CYRI-B mediates internalization of lysophosphatidic acid receptor 1 (LPAR1) uptake through macropinocytosis, thus regulating chemotactic migration of cancer cells towards lysophosphatidic acid (LPA). Although the inclusion of human pancreatic cancer cell lines would have strengthened the study, the work will be of broad interest to cell biologists and the signalling research communities.

  2. eLife

    Reviewer #1 (Public Review):

    In this paper, Nikolaou et al. demonstrated that CYRI-B expression is upregulated in a mouse model of pancreatic ductal adenocarcinoma (PDAC). Interestingly, they found that, while CYRI-B KO promotes the early stages of tumour progression, it prevents the formation of metastasis at later stages. Focusing on the latter, the authors highlight a role for CYRI-B in controlling the membrane availability of the LPA receptor LPAR1, which is required to support PDAC cell chemotaxis towards serum or LPA.

    Strengths: the in vivo and imaging data are very solid, and convincingly support the authors' conclusions. The KPC model is well-established in PDAC research and is a very powerful tool to investigate disease onset and progression. The imaging approaches used are of a very high standard. Good data presentation with the use of super-plots.

    Weaknesses: the authors focused on chemotaxis, but did not present any evidence with regard to the role of CYRI-B in 3D cell invasion, which is a key process associated with cell invasion. The data presented clearly show a specific effect towards liver metastasis, while diaphragm and bowel metastasis were not affected by CYRI-B deletion. It would be beneficial to include a discussion about this, providing some potential explanation behind this observation.

    This work is of interest to cell biologists not only working in pancreatic cancer but also more broadly to researchers interested in vesicular trafficking, plasma membrane receptor dynamics and cell migration.

  3. eLife

    Reviewer #2 (Public Review):

    The manuscript expands on the previous work from the lab where novel interactors of Rac1 GTPase (CYRI-A and B) provide localized inhibition by sequestration of activated Rac1. These novel regulators are fascinating as they complement the functions of the classical negative modulators of GTPases, GAPs and GDIs. The current manuscript focuses on the in vivo role of CYRI-B in pancreatic cancer progression, and distinct CYRI-B functions are shown for early and later stages. The in vivo data following CYRI-B depletion (no change in proliferation, reduced metastatic potential) is substantiated with in vitro analyses of receptor uptake, temporal recruitment of CYRI-B on macropinosomes and reduced chemotaxis.

    The authors describe in detail the role of CYRI-B in pancreatic adenocarcinoma, building from their prior studies mapping CYRI-B function in the regulation of polarity, motility and chemotaxis. The experiments are well-designed and performed, and the text was clearly written. However, the results partially support some of their conclusions. The interpretation of the data and the discussion in the context of human pancreatic tumours would help the understanding and impact of the work.

    The hypothesis is that depletion of CYRI-B would promote localized Rac1 activation at the membrane. However, the authors show that CYRI-B is found overexpressed in PDAC, consistent with other papers where its high expression correlates with poor outcome of many cancers. The prediction is that Rac1 functions modulated by CYRI-B would be inhibited in those tumours where CYRI-B is overexpressed. Is this the case and has it been formally demonstrated?

    Most experiments use the depletion of CYRI-B to probe its function. It would be useful to readers and important to elaborate on how the specific CYRI-B functions shown upon depletion would fit with the in vivo observation of CYRI-B overexpressed in tumours. For example, loss of CYRI-B reduces chemotaxis potential. How this result can be conciliated with the predicted increase in Rac1activation in the absence of CYRI-B? Conversely, a prediction of CYRI-B overexpression in human tumours would imply the inactivation of Rac1 whereas chemotaxis is promoted. The discussion could be improved with the addition of the authors' views and further explanations in this context.

    Similarly, it is confusing to extrapolate a proposed increase in LPAR1 internalization by macropinocytosis with CYRI-B overexpression in PDAC. It is predicted that Rac1 would be locally inhibited in this scenario, and thus micropinocytosis would be compromised. It will be good to spell out what the authors envisage happens. For example, uptake could be switched to another receptor uptake process that would not involve CYRI-B sequestration of Rac1. Discussion of the potential alternatives will strengthen the manuscript.

    "..LPAR1 is a cargo of CYRI-B dependent macropinocytosis" (page 21). This statement reads as an overinterpretation of the specificity of the process. It may suggest that there is a cargo selectivity by CYRI-B, which has not been formally demonstrated or is well accepted. Macropinocytosis is thought to occur as a bulk engulfment of the membrane and thus any receptor at the cell surface would be internalised non-specifically. The demonstrated reduction in LPAR1 uptake could be proportional to the interference with micropinocytosis rate by CYRI-B depletion for example

    Furthermore, the readers would benefit from more clear explanations of the differences and similarities between CYRI-A and CYRI-B. It will be important to clarify the specificity of the proposed functions of each protein. Both localize at the macropinosomes, modulate engulfment and regulate integrin a5b1 trafficking. It will be informative to specify if CYRI-A is also upregulated in human tumours, has a similar outcome as CYRI-B in vivo and also regulates LPAR1 uptake.

    Upon depletion of CYRI-B in pancreatic tumour cells in vivo, the presence of similar levels of jaundice is confusing. Less metastasis is detected in the mesentery. Are liver metastasis affected in the absence of CYRI-B?

  4. eLife

    Reviewer #3 (Public Review):

    The authors first characterize their mouse model of pancreatic cancer and show that CYRI-B mRNA is detectable in pancreatic lesions and that its amount increases over time. They also show that genetic deletion of CYRI-B accelerates pancreatic ductal adenocarcinoma (PDAC), leading to lower survival of mice. This is accompanied by higher levels of phospho-(i.e. activated)-JNK and -ERK, which are likely two of the factors driving cancer cell proliferation. Using in vivo transplantation, the authors further demonstrate that cancer cells depleted for CYRI-B exhibit decreased numbers of metastases in the mesentery, despite showing similar proliferation as control cells.
    Cancer cell migration can be driven by LPA, which binds LPAR1 at the surface of PDAC cells. Investigation of chemotactic migration of cancer cells towards fetal bovine serum as a source of LPA further shows that cancer cells depleted for CYRI-B and expressing GFP as control exhibit strongly reduced chemotactic migration, while cells re-expressing CYRI-B-GFP show normal chemotactic migration. Furthermore, this restored migration is blocked by using the LPAR1/3 inhibitor K116425, showing that CYRI-B is required for the chemotactic migration of PDAC cells in a gradient of serum LPA.

    Using live cell imaging, the authors show that CYRI-B-GFP and LPAR1-mCherry localize to macropinocytic cups and to macropinosomes, indicating that LPAR1 can be internalized by PDAC cells through macropinocytosis. This notion is supported by immunofluorescence analyses showing that PDAC cells depleted for CYRI-B have reduced LPAR1-mCherry internalization upon stimulation with LPA, compared to cells rescued by CYRI-B-GFP expression. Collectively, the authors suggest that CYRI-B regulates macropinocytic uptake of LPAR1, thus regulating the chemotactic migration of PDAC cells towards LPA, which supports the metastasis of pancreatic cancer.

    This is an interesting manuscript that makes a convincing case for the involvement of CYRI-B as a driver of PDAC. A particular strength is the expert use of different mouse models and derived cancer cell lines. The major conclusions are supported by the data presented. The results could be further strengthened by detecting CYRI-B protein (in addition to mRNA) in cancer lesions and also by staining endogenous CYRI-B and LPAR1 in the macropinocytosis experiments.

  5. Version published to 10.1101/2022.11.23.517689v1 on bioRxiv