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.

The Adaptor Protein Bam32 Regulates Rac1 Activation and Actin Remodeling through a Phosphorylation-dependent Mechanism

“…These adaptor proteins bind PI3K lipid products in vitro (22)(23)(24) and are recruited to the plasma membrane in vivo in a PI3K-dependent manner (20,25). Intriguingly, we found that, after BCR stimulation, these adaptor molecules are recruited with delayed and sustained kinetics as compared with Btk (21), and, unlike Btk, their recruitment is not inhibited by the lipid phosphatase SHIP (SH2-containing inositol phosphatase) (26).…”

Human papillomaviruses, cervical cancer and cell polarity

“…It is a multiple PDZ-containing protein, with 13 PDZ domains (Ullmer et al, 1998), and it is thought to be involved in the selective targeting and assembly of signalling complexes (Becamel et al, 2000). In polarized epithelial cells, it localizes to tight junctions through the Coxsackie and adenovirus receptor (Coyne et al, 2004), where it interacts with the members of the Claudin and JAM (junctional adhesion molecule) families and may be involved in cell polarity signalling, tight junction barrier function and osmotic stress responses (Hamazaki et al, 2001;Kimber et al, 2002;Jeansonne et al, 2003;Lanaspa et al, 2007).…”

The Coxsackievirus and Adenovirus Receptor Interacts with the Multi-PDZ Domain Protein-1 (MUPP-1) within the Tight Junction

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