Review Question Answers

1. T. cruzi enter a host cell by a process that is:
   a) dependent on host cell actin polymerization
   b) dependent on host cell microtubules
   b
   
   
2. How did studying the entry mechanism of T. cruzi lead to a better understanding of normal cellular function(s)?
   It lead to the discovery that the behavior of conventional lysosomes in mammalian cells is controlled by cytosolic calcium concentrations and that there is a population of peripheral lysosomes that is near the plasma membrane that function more as calcium-regulated secretory vesicles rather terminal compartments of the endocytic pathway, which was thought previously.
   
   
3. Synaptotagmin (Syt) is:
   a) an enzyme that cleaves disulfide bonds
   b) a protein produced by Leishmania that causes membrane fusion
   c) a protein that couples calcium concentrations with membrane fusion
   d) a glycoprotein that in involved in nuclear transport
   c
   
   
4. True/False   If you mutate or change parts of Syt VII, T. cruzi is still able to invade host cells and replicate intracellularly.
   False
   
   
5. When T. cruzi invades the host cell, it acquires a membrane that is derived from the host cell.  Where does it come from?
   lysosome membranes
   
   
6. Lysosomal fusion with the plasma membrane is also important in the retention of the parasite inside the host cell.  How do we know this?
   When you inhibit lysosomal fusion, the entry of the parasite is reversible.  By using the lysosomal membranes to surround itself, the parasite can anchor itself to the microtubules within the cell (because lysosomes have proteins on their surfaces that interact with microtubules and anchor them).
   
   
7. The normal function of lysosomes is to degrade proteins, but in the case of T. cruzi, this doesn’t seem to happen because the parasite is not degraded even though it is living in a lysosomal like compartment (acidic with lysosomal proteins).  What other parasite(s) do/does this same thing?
   Leishmania spp
   
   
8. Where does Leishmania replicate within the cell?
   Lysosomal compartments
   
   
9. Nramp1 and Nramp2 are host proteins that are responsible for depleting iron from within endocytic compartments.  Why are these proteins important?
   
   The most important function is to transport iron to the cytosol for the cell to use it in normal cellular processes.  Secondarily, this is a defense mechanism of the host cell.  Since almost all known pathogens require iron to grow well, if the lysosome is deficient in iron, then there is very little iron available for the parasite to use to grow and theoretically it would die, thus preventing an infection.
   
   
10. What is LIT 1?
    Leishmania Iron Transport protein
    
    
11. If the host is depleting the iron that is in the lysosomal compartments by using Nramp1 and Nramp 2, how does Leishmania acquire iron?
    a) by using the Na+/K+ pump
    b) by using LIT1
    c) by diffusion
    d) by degrading Nramp1 and Nramp2
    b
    
    
12. Do LIT1 -/- mutants cause lesions in mice?  Can parasites be isolated from host tissues?
    No; Yes
    
    
13. Do we know in which cell types Leishmania persists in host tissue?
    It is still unknown in which cell types Leishmania persists within the host tissues.