Evidence that the tandem-pleckstrin-homology-domain-containing protein TAPP1 interacts with Ptd(3,4)P2 and the multi-PDZ-domain-containing protein MUPP1 in vivo

Abstract

PtdIns(3,4,5)P3 is an established second messenger of growth-factor and insulin-induced signalling pathways. There is increasing evidence that one of the immediate breakdown products of PtdIns(3,4,5)P3, namely PtdIns(3,4)P2, whose levels are elevated by numerous extracellular agonists, might also function as a signalling molecule. Recently, we identified two related pleckstrin-homology (PH)-domain-containing proteins, termed 'tandem-PH-domain-containing protein-1' (TAPP1) and TAPP2, which interacted in vitro with high affinity with PtdIns(3,4)P2, but did not bind PtdIns(3,4,5)P3 or other phosphoinositides. In the present study we demonstrate that stimulation of Swiss 3T3 or 293 cells with agonists that stimulate PtdIns(3,4)P2 production results in the marked translocation of TAPP1 to the plasma membrane. This recruitment is dependent on a functional PtdIns(3,4)P2-binding PH domain and is inhibited by wortmannin, a phosphoinositide 3-kinase inhibitor that prevents PtdIns(3,4)P2 generation. A search for proteins that interact with TAPP1 identified the multi-PDZ-containing protein termed 'MUPP1', a protein possessing 13 PDZ domains and no other known modular or catalytic domains [PDZ is postsynaptic density protein (PSD-95)/Drosophila disc large tumour suppressor (dlg)/tight junction protein (ZO1)]. We demonstrate that immunoprecipitation of endogenously expressed TAPP1 from 293-cell lysates results in the co-immunoprecipitation of endogenous MUPP1, indicating that these proteins are likely to interact with each other physiologically. We show that TAPP1 and TAPP2 interact with the 10th and 13th PDZ domain of MUPP1 through their C-terminal amino acids. The results of the present study suggest that TAPP1 and TAPP2 could function in cells as adapter proteins to recruit MUPP1, or other proteins that they may interact with, to the plasma membrane in response to signals that elevate PtdIns(3,4)P2.

Role of TAPP1 and TAPP2 adaptor binding to PtdIns(3,4)P2 in regulating insulin sensitivity defined by knock-in analysis

“…To date, TAPP1 and TAPP2 have been reported to interact via their C-terminal residues with at least three PDZ-domain-binding proteins, including PTPN13 (known previously as PTPL1 or FAP-1) [23], as well as the scaffolding proteins MUPP1 [20], syntrophin [24] and utrophin [25]. PTPN13 [40], MUPP1 [41], syntrophin and utrophin [42] are known to interact with a large number of binding partners involved in regulating numerous signalling pathways, so it may not be straightforward to deconvolute which of these is involved in regulating insulin sensitivity.…”

“…Mutation of the alanine residue to glycine in TAPP1 resulted in it being capable of interacting with PtdIns(3,4,5) P 3 and PtdIns(3,4) P 2 with similar affinity [19]. Evidence also suggests that TAPP1 binds PtdIns(3,4) P 2 selectively in vivo , as TAPP1 relocated from the cytosol to the plasma membrane of cells following stimulation with agonists that induced PtdIns(3,4) P 2 , but not with those that induced mainly PtdIns(3,4,5) P 3 [20]. Similarly, in B-cells, both TAPP1 and TAPP2 translocated to the plasma membrane in response to antigen stimulation and this correlated with the formation of PtdIns(3,4) P 2 rather than production of PtdIns(3,4,5) P 3 [21,22].…”

“…Apart from the PH domains, the only other known functional region is a C-terminal PDZ-binding motif that interacts with several PDZ-binding proteins, including PTPN13 (known previously as PTPL1 or FAP-1) [23] as well as the scaffolding proteins MUPP1 (multiple PDZ-domain-containing protein 1) [20], syntrophin [24] and utrophin [25]. One hypothesis was that TAPP1 and TAPP2, by specifically recognizing PtdIns(3,4) P 2 , could function to recruit signalling molecules or complexes to the plasma membrane that down-regulate the PI3K signalling pathways [23].…”

Perspectives for using genetically encoded fluorescent biosensors in plants

“…Using this sensor, auxin distribution was mapped during gravity sensing and lateral shoot formation in Arabidopsis. For mammalian cells, e.g., a variety of GFP-based biosensors exist for kinases, GTPases, phosphatidylinositols (PtdIns) (Kimber et al, 2002; Yoshizaki et al, 2006; Zhang and Allen, 2007). Such sensors (PtdIns) have only recently emerged in the plant community (Munnik and Nielsen, 2011), probably because plants use different signaling components that cannot be targeted by sensors developed for mammalian systems.…”

Cell polarity proteins: common targets for tumorigenic human viruses

“…Although TJ-associated MAGI-1 and MUPP1, a paralog of the PATJ polarity protein (Lemmers et al ., 2002; Michel et al ., 2005; Shin et al ., 2005), are involved in the assembly of membrane signaling complexes (Barritt et al ., 2000; Becamel et al ., 2001; Hamazaki et al ., 2002; Kimber et al ., 2002; Laura et al ., 2002; Patrie et al ., 2002; Hirabayashi et al ., 2003; Jeansonne et al ., 2003; Murata et al ., 2005; Heydecke et al ., 2006; Sakurai et al ., 2006; Balasubramanian et al ., 2007; Sugihara-Mizuno et al ., 2007), it is not yet known whether these two PDZ proteins likewise function in TJ assembly and apical–basal polarity establishment (Figure 3). In addition to their aberrant sequestration by Ad9 E4-ORF1 in insoluble cytoplasmic complexes, MAGI-1 and MUPP1 bind to and are targeted for proteasome-mediated degradation by high-risk HPV E6 (Glaunsinger et al ., 2000; Lee et al ., 2000).…”