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Figure 9 | BMC Microbiology

Figure 9

From: Evidence from bioinformatics, expression and inhibition studies of phosphoinositide-3 kinase signalling in Giardia intestinalis

Figure 9

Proposed model for PI metabolism and PI3K signalling in G. intestinalis. A model of PI3K signalling in G. intestinalis based on known mechanisms in mammalian cells and yeast. GiPI3K1 and GiPI3K2 are suggested to localise at the plasma membrane and GiPI3K2 at some undefined intracellular compartment. Proteins that may participate in G. intestinalis PI metabolism have been identified and are shown (as indicated by numbering): (1) MTM (Myotubularin, GenPept: EAA37232 or EAA38552), (2) PIPkin (Phosphatidylinositol phosphate kinase, GenPept: EAA42556), (3) PI 5-phosphatase (GenPept: EAA40147), (4) PTEN (Phosphatase and tensin homolog, GenPept: EAA42276), (5) PI4K (Phosphoinositide 4-kinase, GenPept: EAA38121). The question mark indicates a possible 4-phosphatase of unknown identity. PtdIns(3)P possibly recruits PX and FYVE -domain-containing proteins, of which there are several encoded in the G. intestinalis genome (PX-domain proteins: EAA39579, EAA42255, EAA42811, EAA42799 are possible sorting nexins; FYVE-domain protein: EAA42608, a possible endofin). A putative giardial PDK1 (3-phosphoinositide-dependent protein kinase, GenPept: EAA38977) may be recruited to PtdIns(3,4,5)P3. Other previously characterised giardial signalling components which may be invoked could include: GiPKB [6], gPKA [2], g14-3-3 [46], gTOR [47] and gERK1 and gERK2 [5]. Not shown in this figure is the possible generation of PtdIns(3,4)P2 from PtdIns(4)P by GiPI3K1.

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