Leishmania donovani infection enhances lateral mobility of macrophage membrane protein which is reversed by liposomal cholesterol

Background

The protozoan parasite Leishmania donovani (LD) reduces cellular cholesterol of the host possibly for its own benefit. Cholesterol is mostly present in the specialized compartment of the plasma membrane. The relation between mobility of membrane proteins and cholesterol depletion from membrane continues to be an important issue. The notion that leishmania infection alters the mobility of membrane proteins stems from our previous study where we showed that the distance between subunits of IFNγ receptor (R1 and R2) on the cell surface of LD infected cell is increased, but is restored to normal by liposomal cholesterol treatment.

Methodology/Principal Findings

We determined the lateral mobility of a membrane protein in normal, LD infected and liposome treated LD infected cells using GFP-tagged PLCδ1 as a probe. The mobility of PLCδ1 was computationally analyzed from the time lapse experiment using boundary distance plot and radial profile movement. Our results showed that the lateral mobility of the membrane protein, which is increased in infection, is restored to normal upon liposomal cholesterol treatment. The results of FRAP experiment lent further credence to the above notion. The membrane proteins are intimately linked with cellular actin and alteration of cellular actin may influence lateral mobility. We found that F-actin is decreased in infection but is restored to normal upon liposomal cholesterol treatment as evident from phalloidin staining and also from biochemical analysis by immunoblotting.

Conclusions/Significances

To our knowledge this is the first direct demonstration that LD parasites during their intracellular life cycle increases lateral mobility of membrane proteins and decreases F-actin level in infected macrophages. Such defects may contribute to ineffective intracellular signaling and other cellular functions.

The protozoan parasites, Leishmania donovani, replicate within the macrophages of the mammalian hosts. During its intracellular lifecycle, the parasite induces a wide variety of defects in the membrane homeostasis. Membrane bound receptor molecules are important for interacting with external stimuli. Our study very clearly showed that there is an increase in the mobility of membrane protein coupled with decrease in F-actin in infected cells, which may be corrected by liposomal cholesterol treatment. This observation indicates that intracellular parasite may alter the membrane biology of infected cells which may dampen overall cellular function.