Glycocalyx-mediated Cell Adhesion and Migration

Ankita Jha, Post-doctoral research fellow, National Institutes of Health (NIH), Bethesda, USA (Cell migration, cytoskeleton, plasma membrane organization)

Adam Shellard, Postdoc, University College London, UK

Rebecca Kirk, Associate Editorial Director, PLOS (publishing, structural biology, biochemistry)

Joseph Jose Thottacherry, Postdoc, Gurdon Institute, Univ of Cambridge, UK

This review was done collaboratively as a part of #preprintreviewchallenge by ASAP Bio

 

We would like to thank Rebecca for all her inputs on our reviewing process and noting down all the discussion points.

Overview and take home message- Integrin signaling based adhesion is one of the key components in regulating mesenchymal cell migration. Cells can adapt to different modes of motility as a result of their interaction with the environment. Low levels of integrin and higher contractility promote amoeboid or bleb based migration. This work focuses on identifying cellular components that regulate integrin independent cell and matrix interactions. Authors show that in low integrin availability cells can utilize cell surface glycocalyx to mediate cell-matrix interactions. This work widens the understanding of the role of cell surface glycans in cell migration, Glycan-based adhesions are in the force range of 100-500 pN. Glycans are associated with cellular protrusions and blebs.

What we liked about the work- This work is a basic detective work in cell biology that shows the alternative cellular components that are involved in cell-matrix interactions in absence of integrins. It starts to provide some details about the ‘stickiness’ associated with the glycocalyx that can mediate integrin independent adhesion.

Major points-

1. Measurement of the three cell lines is described, but there is no consistent visualisation to enable rapid comparison. Blocking or knocking down  integrin in MV3 (melanoma cells) leads to decrease in the speed of migration while in non-cancer cells MEFs (fibroblasts) increases the speed of migration, is this due to differential change in contractility? Offering an explanation of the difference in behaviour of the cells lines would be helpful. 
2. What happens to the overall contractility of cells with glycan removal, decrease in contractility can account for decrease in the bleb like protrusions or enough force generation to move in collagen, thus decrease in the motility of cells. Possible experiment to do would be the contractility index measurements between polyacrylamide gels ( Callan-Jones and Voituriez 2013).
3. Authors use three different cell lines to show the effect of glycan removal on migration, but they only looked at levels of proteo-glycan cell surface receptors like syndecan-1, CD44 etc in MV3 cells. They perturb CD44 in MV3 cells but not in other cell types. They also perturb the function of CD44 by using antibody Hermes-1. Hermes-1 epitope recognizes the hyaluronate binding site of CD44 (Aho et al 1994) but it does not eliminate the function of CD44 in MV3 cells. CD44 is a glycoprotein that might still have ‘stickiness’ even after Hermes-1 treatment. Better experiment would have been to knockdown CD44 in MV3 cells.
4. Fig 2b: In the description, it says ‘additional treatment of B1-4 galactosidase strongly reduced glycocalyx thickness’ – i don’t know if they have shown the glycocalyx thickness for P/N vs P/N/G treatment somewhere else but its not in Fig 2b. Since P/N seems to not do much but P/N/G is dramatic (for migration: Fig 3c/d), this might be useful. Also, does it make sense to do b1-4 galactosidase treatment alone ?
5. Fig 4f:  Why does force not increase with increasing interaction time for b1/b3 kO unlike w/ p/n/g – or why does the force increase with p/n/g over time. Not clear ?Possible expt-  traction force measurement with cRGD 4B4 and w/ P/N/G  would have been straight forward.
6. Integrins are heavily glycosylated and have interaction with other glycans in the ECM? (review Marsico et al 2018). Do authors have an explanation to why they do not see an effect on integrin dependent migration after P/N/G removal? 
7. Fig 5 – Text has a missing clarification of detection of polarity and interpretation of this information. If the cells are motile, this would allow detection of polarity for those cells; but for those that have been inhibited how was the polarity assigned? What parameter are we using to define moving and non-moving blebs?
8. In figure 5b, the lack of elongation for MEFs, and the description of the filopodia structure, this lacked context. The figure, graph and description is confusing since the authors describe mesenchymal migration vs bleb, filopodia etc. Mesenchymal is a mode of motility which can have lamellopodia, filopodia etc like protrusions. Rest of the graph is based on the type of protrusions. It lacks clarity.

Minor points-

Selection of cancer lines, and a non cancer line and the additional integrin-independent migrating cell line with a KD was interesting. The overall detail, and the validation, and the repeating with multiple cells lines, means that there is a lot of information to absorb on first reading, which can  be improved. Glycan removal certainly has  an effect on the cell migration behaviour, but the mechanism is less established.

• Fig1a result in text – doesn’t match figure? Fig. 1 – integrin KD only mildly inhibits migration – is this because it is not a full KO?
• Fig 2 legend – blue dot? (I guess they mean green). Define IC/EC (intracellular/extracellular compartment?)
• Fig. 3H – initially unclear what yellow % numbers were – better to just have smaller data point dots 1
• Figure 3 a- Missing control figure for the trajectory of MV3 cells with cRAD and no enzymatic treatment. Authors mention in Page 6,  that MV3 cells expressing integrins after enzymatic action (P/N/G) show baseline migration though the trajectory data is not shown. 
• Page 4 para 1 – mentioned traction forces. Data?

• Fig. 5F – not mentioned/discussed? What’s the significance?
• Page 5 para 1 – TEM analysis of MV3 cells- extended data Fig 4b does not show TEM.
• How do authors differentiate between glycans and cell surface receptors in TEM?
• The step-wise requirement for the glycosidase treatment lacks clarity.

Additional comments / questions to the authors-

The authors propose that there is a cell-type specific of glycans for maintaining migration – do they have an opinion on why this might be? Can this be somewhat explained by the variability of the AFM results, and the composition of the glycocalyx in different cells?

Discussion between the reviewers-

Point 1

AJ – This has been done previously in terms of analysis of motility with integrin KD. Offering an explanation of the difference in behaviour of the cells lines would be helpful. 

AS – point is that the fact that it has an effect on the behaviour?

JT – the choice of cell lines is of interests; the integrin expression

AJ – the contractility will have an impact on the behaviour of these cells.

Point 2

JT – they could have simplified this perhaps, and the in vivo work might not be a requirement

AS – this would explain the behaviour in mammals, but what about other analogous structures in other organisms? So, is this specific to mammalian cells? No, it seems not- but there are specific glycans for particular cells that might have an influence.

AJ – thinking about the mechanism, there are other immune cells that are known to ‘paddle’ with the TM proteins.

Point 3

AJ – the lack of elongation for MEFs, and the description of the filopodia structure, this lacked context. KD of MEFs already had blebbing, and so where did this come from

AS – in 5b, what does that mean, it’s not a type of protrusion, it is a type of cell. Non-moving vs moving; AS agrees with the point from AJ.

AJ –  does lack of glycans affect MMP function/degradation? This can be important in cancer cells – they then might become less motile with a lack of MMP secretion?

Tags: #cancerbiology, #cellmigration, asapbio, glycobiology

doi: https://doi.org/10.1242/prelights.24944

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