This diagram summarizes our understanding of the proteins involved in the actin

Question

This diagram summarizes our understanding of the proteins involved in the actin polymerization that moves Listeria inside the mammalian cell cytosol (Nat Rev Mole Cell Boil 1, 110-9, 2000) Please notice that Listeria is using many of the actin-related proteins we have talked about in class in order to move (Listeria is hijacking those proteins), and only one of the proteins is indeed a Listeria protein, Act A. We know this protein is necessary and sufficient for actin polymerization in this context. To demonstrate that Act A is sufficient, scientists expressed heterologously Act A in a non-pathogenic specie of Listeria, Listeria innocuous. Wild type L. innocuous is unable to polymerize actin and as a consequence unable to propagate the infection between cells (this is why it is non-pathogenic). Q6 How will you design the experiment using L. innocuous to demonstrate that Act A is sufficient to induce actin polymerization? What is the control? What is the perturbation? What parameter are you going to measure? If you do not have access to a microscope, what parameter could you measure?

Explanation / Answer

L.innocua is a non-pathogenic Listeria species, unlike its pathogenic counterparts which infect humans. The mode of pathogenesis of the infective Listeria species is that they possess a protein called ActA, which aid in actin polymerization inside the host. In this way the pathogenic Listeria species propel through the human host cells.

ActA or Actin assembly inducing protein, interacts with Arp2/3 complex and actin monomers, to aid in actin polymerization on towards the bacterial surface and help the bacterial spread. It has been shown by research that, ActA is not only necessary but also solely sufficient to induce actin polymerization. Likewise, L.innocua lacks this ActA protein, thus it is non-pathogenic.

Experiment design

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