The Pleckstrin Homology Domain of PLCδ1 Exhibits Complex Dissociation Properties at the Inner Leaflet of Plasma Membrane Sheets

Author(s):  
Madeline R. Sponholtz ◽  
Eric N. Senning
2004 ◽  
Vol 24 (3) ◽  
pp. 1245-1255 ◽  
Author(s):  
Alexias Safi ◽  
Marie Vandromme ◽  
Sabine Caussanel ◽  
Laure Valdacci ◽  
Dominique Baas ◽  
...  

ABSTRACT In this work, we report the implication of the pleckstrin homology (PH) domain-containing protein CKIP-1 in phosphatidylinositol 3-kinase (PI3-K)-regulated muscle differentiation. CKIP-1 is upregulated during muscle differentiation in C2C12 cells. We show that CKIP-1 binds to phosphatidylinositol 3-phosphate through its PH domain and localizes to the plasma membrane in a PI3-K-dependent manner. Activation of PI3-K by insulin or expression of an active form of PI3-K p110 induces a rapid translocation of CKIP-1 to the plasma membrane. Conversely, expression of the 3-phosphoinositide phosphatase myotubularin or PI3-K inhibition by LY294002, wortmannin, or mutant p85 abolishes CKIP-1 binding to the membrane. Upon induction of differentiation in low-serum medium, CKIP-1 overexpression in C2C12 myoblasts first promotes proliferation and then stimulates the expression of myogenin and cell fusion in a manner reminiscent of the dual positive effect of insulin-like growth factors on muscle cells. Interference with the PI3-K pathway impedes the effect of CKIP-1 on C2C12 cell differentiation. Finally, silencing of CKIP-1 by RNA interference abolishes proliferation and delays myogenin expression. Altogether, these data strongly implicate CKIP-1 as a new component of PI3-K signaling in muscle differentiation.


2002 ◽  
Vol 363 (3) ◽  
pp. 657-666 ◽  
Author(s):  
Stephen A. WATT ◽  
Gursant KULAR ◽  
Ian N. FLEMING ◽  
C. Peter DOWNES ◽  
John M. LUCOCQ

Ptd(4,5)P2 is thought to promote and organize a wide range of cellular functions, including vesicular membrane traffic and cytoskeletal dynamics, by recruiting functional protein complexes to restricted locations in cellular membranes. However, little is known about the distribution of PtdIns(4,5)P2 in the cell at high resolution. We have used the pleckstrin homology (PH) domain of phospholipase δ1 (PLCδ1), narrowly specific for PtdIns(4,5)P2, to map the distribution of the lipid in astrocytoma and A431 cells. We applied the glutathione S-transferase-tagged PLCδ1 PH domain (PLCδ1PH—GST) in an on-section labelling approach which avoids transfection procedures. Here we demonstrate PtdIns(4,5)P2 labelling in the plasma membrane, and also in intracellular membranes, including Golgi (mainly stack), endosomes and endoplasmic reticulum, as well as in electron-dense structures within the nucleus. At the plasma membrane, labelling was more concentrated over lamellipodia, but not in caveolae, which contained less than 10% of the total cell-surface labelling. A dramatic decrease in signal over labelled compartments was observed on preincubation with the cognate headgroup [Ins(1,4,5)P3], and plasma-membrane labelling was substantially decreased after stimulation with thrombin-receptor-activating peptide (SFLLRN in the one-letter amino acid code), a treatment which markedly diminishes PtdIns(4,5)P2 levels. Thus we have developed a highly selective method for mapping the PtdIns(4,5)P2 distribution within cells at high resolution, and our data provide direct evidence for this lipid at key functional locations.


1997 ◽  
Vol 272 (45) ◽  
pp. 28447-28454 ◽  
Author(s):  
Jord C. Stam ◽  
Eva E. Sander ◽  
Frits Michiels ◽  
Frank N. van Leeuwen ◽  
Hendrie E. T. Kain ◽  
...  

2008 ◽  
Vol 283 (28) ◽  
pp. 19836-19844 ◽  
Author(s):  
Eric Macia ◽  
Mariagrazia Partisani ◽  
Cyril Favard ◽  
Eva Mortier ◽  
Pascale Zimmermann ◽  
...  

2004 ◽  
Vol 382 (3) ◽  
pp. 857-865 ◽  
Author(s):  
Ian N. FLEMING ◽  
Ian H. BATTY ◽  
Alan R. PRESCOTT ◽  
Alex GRAY ◽  
Gursant S. KULAR ◽  
...  

Binding of the Rac1-specific guanine-nucleotide-exchange factor, Tiam1, to the plasma membrane requires the N-terminal pleckstrin homology domain. In the present study, we show that membrane-association is mediated by binding of PtdIns(4,5)P2 to the pleckstrin homology domain. Moreover, in 1321N1 astrocytoma cells, translocation of Tiam1 to the cytosol, following receptor-mediated stimulation of PtdIns(4,5)P2 breakdown, correlates with decreased Rac1-GTP levels, indicating that membrane-association is required for GDP/GTP exchange on Rac1. In addition, we show that platelet-derived growth factor activates Rac1 in vivo by increasing PtdIns(3,4,5)P3 concentrations, rather than the closely related lipid, PtdIns(3,4)P2. Finally, the data demonstrate that PtdIns(4,5)P2 and PtdIns(3,4,5)P3 bind to the same pleckstrin homology domain in Tiam1 and that soluble inositol phosphates appear to compete with lipids for this binding. Together, these novel observations provide strong evidence that distinct phosphoinositides regulate different functions of this enzyme, indicating that local concentrations of signalling lipids and the levels of cytosolic inositol phosphates will play crucial roles in determining its activity in vivo.


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