Protein-protein interactions of the GIMAP GTPases

As stated above, very little is known as yet about the biochemical mechanisms by which GIMAP GTPases exert their functional effects. In an attempt to address this knowledge gap directly, we undertook experiments to identify protein binding partners of the GIMAPs.

Different approaches that we have tried include direct immunoprecipitation of GIMAP-protein complexes, affinity purification using GST-GIMAP fusion protein pull-downs from cell or tissue extracts and tag-mediated affinity purification using engineered GIMAP constructs.

Using a tagged version of human GIMAP6 we have recently identified an interaction of this GIMAP family member with an autophagy-related protein named GABARAPL2 (or GATE-16).

Taking this observation further, we have shown that human GIMAP6 relocates from the cytosol of cells to the autophagosomes in reponse to starvation conditions. This finding raises the possibility that this, and perhaps some other, GIMAP GTPases may regulate aspects of autophagy (Pascall et al. 2013).