Phosphatidylinositol-3,4-Bisphosphate and Its Binding Protein Lamellipodin Regulate Chemotaxis of Malignant B Lymphocytes

Abstract

Cell migration is controlled by PI3Ks, which generate lipid messengers phosphatidylinositol-3,4,5-trisphosphate and phosphatidylinositol-3,4-bisphosphate [PI(3,4)P2] and consequently recruit pleckstrin homology (PH) domain–containing signaling proteins. PI3K inhibition impairs migration of normal and transformed B cells, an effect thought to partly underlie the therapeutic efficacy of PI3K inhibitors in treatment of B cell malignancies such as chronic lymphocytic leukemia. Although a number of studies have implicated phosphatidylinositol-3,4,5-trisphosphate in cell migration, it remains unknown whether PI(3,4)P2 plays a distinct role. Using the PI(3,4)P2-specific phosphatase inositol polyphosphate 4-phosphatase, we investigate the impact of depleting PI(3,4)P2 on migration behavior of malignant B cells. We find that cells expressing wild-type, but not phosphatase dead, inositol polyphosphate 4-phosphatase show impaired SDF-induced PI(3,4)P2 responses and reduced migration in Transwell chamber assays. Moreover, PI(3,4)P2 depletion in primary chronic lymphocytic leukemia cells significantly impaired their migration capacity. PI(3,4)P2 depletion reduced both overall motility and migration directionality in the presence of a stable chemokine gradient. Within chemotaxing B cells, the PI(3,4)P2-binding cytoskeletal regulator lamellipodin (Lpd) was found to colocalize with PI(3,4)P2 on the plasma membrane via its PH domain. Overexpression and knockdown studies indicated that Lpd levels significantly impact migration capacity. Moreover, the ability of Lpd to promote directional migration of B cells in an SDF-1 gradient was dependent on its PI(3,4)P2-binding PH domain. These results demonstrate that PI(3,4)P2 plays a significant role in cell migration via binding to specific cytoskeletal regulators such as Lpd, and they suggest that impairment of PI(3,4)P2-dependent processes may contribute to the therapeutic efficacy of PI3K inhibitors in B cell malignancies.

The impact of phosphoinositide 5-phosphatases on phosphoinositides in cell function and human disease

“…For example, in B cells, SHIP1 catalyzes an important production of PI(3,4)P 2 . Evidence has been provided that PI(3,4)P 2dependent processes may contribute to the therapeutic efficacy of PI 3-kinase inhibitors in B-cell malignancies (23). The role of SHIP1 is different in T cells, where it can have multiple functions [reviewed in (24)].…”

Phosphoinositides modulate the voltage dependence of two-pore channel 3

“…PI(3,4)P 2 is produced by PI3-kinase (PI3K) from PI(4)P, as is Phosphatidylinositol (3,4,5)-trisphosphate (PIP 3 ), which is also known to be an important signaling PI, as represented by Akt activation ( Manning and Toker, 2017 ). Although PI(3,4)P 2 has received less attention, several emerging pieces of evidence have indicated the unique and critical importance of PI(3,4)P 2 , such as in spatially localized PI3K signaling ( Braccini et al, 2015 ), endocytosis ( Posor et al, 2013 ; Boucrot et al, 2015 ), neuronal death ( Sasaki et al, 2010 ), membrane ruffling ( Hogan et al, 2004 ), and cell migration ( Bae et al, 2010 ; Li et al, 2016 ). PI(3,4)P 2 has been known to bind some membrane-associated proteins ( Hogan et al, 2004 ; Li and Marshall, 2015 ).…”

PI(3,4)P2 plays critical roles in the regulation of focal adhesion dynamics of MDA‐MB‐231 breast cancer cells

“…Increasing evidence suggests that PI(3,4)P 2 , which is generated from PIP 3 , not only induces the activation of Akt, but can act independently to regulate processes such as of membrane ruffle formation, podosome formation, lamellipodia formation, and lamellipodia maturation . Recent study showed that PI(3,4)P 2 depletion impairs motility during B cell chemotaxis, and that Lpd, whose PH domain specifically binds to PI(3,4)P 2 , co‐localizes with PI(3,4)P 2 to mediate directional migration . Thus, PI(3,4)P 2 is an important signaling molecule that is involved in regulating cytoskeletal rearrangements at the plasma membrane .…”

“…(35) Recent study showed that PI(3,4)P 2 depletion impairs motility during B cell chemotaxis, and that Lpd, whose PH domain specifically binds to PI(3,4)P 2 , co-localizes with PI(3,4)P 2 to mediate directional migration. (36) Thus, PI(3,4)P 2 is an important signaling molecule that is involved in regulating cytoskeletal rearrangements at the plasma membrane. (37) Other studies have demonstrated the role of Lpd in the actin cytoskeletal network.…”