What do intermediate filaments do

Actin cytoskeleton only?

1) Can cells survive without one of the various cytoskeletal components?

Yes for sure. For actin and microtubules (MTs) at least, there are many eukaryotic cell types that can survive without them. MTs can be disturbed by cold shock (see for example here https://www.ncbi.nlm.nih.gov/pubmed/16505977). How well the cell survives depends on the cell type, but the ability to survive without MTs can range from minutes to hours, as far as I know. Once the temperature is back to normal, the MTs simply grow back again. Of course, the cells do not behave normally in the meantime as many processes depend on MTs. Actin can be destroyed with various drugs or genetic constructs or cut with femtosecond lasers (see for example https://www.ncbi.nlm.nih.gov/pubmed/28324605). Again, many processes are disrupted, especially cell motility, but most cells can survive for a while without actin.

I do not know whether there are eukaryotic cells that have no intermediate filaments or at least can survive without them for some time.

2) Could a cell function normally if some type of cytoskeletal component is missing?

First, as far as I know, there is no eukaryotic cell without MTs or actin. We usually use actin and tubulin promoters for transgenes and we assume that all cells express them. So I am taking this question hypothetically.

As with any hypothetical question, the answer then depends only on the constraints you define. Can the cell have any new proteins that do not currently exist? Then you could definitely get eukaryotic cells with only MTs or only actin or only intermediate filaments. You just have to bend all the other things the cell does to match this type of filament and then happily argue about whether or not this is still a eukaryotic cell.

But I think Actin would find it easier to take on the other filaments' jobs than the other way around.

MTs are big and rigid. They cannot operate on scales below 25 nm like actin, and the individual tubulin dimers cannot do anything useful until a tube of minimal length has been formed from many dimers. Interfilament monomers are quite thin, but very long. Actin monomers are small and spherical, and a super-short actin filament made from a handful of monomers can function as a filament, branch, form networks, attract things, etc. Actin-mediated endocytosis depends crucially on it (https: // www .ncbi.nlm.nih. gov / pubmed / 25675087 for example). It would be difficult to find workarounds for these little functions of actin if MTs or IFs were to replace them. On the other hand, actin filaments can very easily be processed into large, thick, rigid rods like microtubules. Many types of cells do this all the time as they form filopodia. Actin nets can also provide mechanical support (both stable and flexible) similar to that of IF nets. With minor shifts in the regulation of where, when, and how filaments should be organized, actin could likely take over the functions of the other cytoskeletons. It would probably require a rather sophisticated regulatory system to perform all of the different functions in one cell at the same time.


@EliKorvigo Noted, thanks for the correction.