title: 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.
authors.affiliation: Department of Immunology, University of Manitoba, Winnipeg, Manitoba R3E 0T5, Canada;
authors.forename: Hongzhao
authors.identifier: http://orcid.org/0000-0002-1587-8866
authors.initials: H
authors.lastname: Li
authors.affiliation: Department of Immunology, University of Manitoba, Winnipeg, Manitoba R3E 0T5, Canada;
authors.forename: Xun
authors.initials: X
authors.lastname: Wu
authors.affiliation: Department of Immunology, University of Manitoba, Winnipeg, Manitoba R3E 0T5, Canada;
authors.forename: Sen
authors.identifier: http://orcid.org/0000-0001-8287-8981
authors.initials: S
authors.lastname: Hou
authors.affiliation: Babraham Institute, Cambridge CB22 3AT, United Kingdom;
authors.forename: Mouhannad
authors.identifier: http://orcid.org/0000-0002-7523-7593
authors.initials: M
authors.lastname: Malek
authors.affiliation: Babraham Institute, Cambridge CB22 3AT, United Kingdom;
authors.forename: Anna
authors.identifier: http://orcid.org/0000-0002-3832-8795
authors.initials: A
authors.lastname: Kielkowska
authors.affiliation: Department of Immunology, University of Manitoba, Winnipeg, Manitoba R3E 0T5, Canada;
authors.forename: Edward
authors.identifier: http://orcid.org/0000-0001-9950-7941
authors.initials: E
authors.lastname: Noh
authors.affiliation: Department of Immunology, University of Manitoba, Winnipeg, Manitoba R3E 0T5, Canada;
authors.forename: Kennedy J
authors.identifier: http://orcid.org/0000-0002-6509-8817
authors.initials: KJ
authors.lastname: Makondo
authors.affiliation: Manitoba Centre for Proteomics and Systems Biology, Winnipeg, Manitoba R3E 3P4, Canada;
authors.forename: Qiujiang
authors.initials: Q
authors.lastname: Du
authors.affiliation: Manitoba Centre for Proteomics and Systems Biology, Winnipeg, Manitoba R3E 3P4, Canada; Department of Internal Medicine, University of Manitoba, Winnipeg, Manitoba R3E 3P4, Canada; Department of Biochemistry and Medical Genetics, University of Manitoba, Winnipeg, Manitoba R3E 0T5, Canada;
authors.forename: John A
authors.identifier: http://orcid.org/0000-0002-5465-446X
authors.initials: JA
authors.lastname: Wilkins
authors.affiliation: Department of Internal Medicine, University of Manitoba, Winnipeg, Manitoba R3E 3P4, Canada; Research Institute in Oncology and Hematology, Winnipeg, Manitoba R3E 0V9, Canada; and.
authors.forename: James B
authors.initials: JB
authors.lastname: Johnston
authors.affiliation: Department of Immunology, University of Manitoba, Winnipeg, Manitoba R3E 0T5, Canada; Department of Biochemistry and Medical Genetics, University of Manitoba, Winnipeg, Manitoba R3E 0T5, Canada; Research Institute in Oncology and Hematology, Winnipeg, Manitoba R3E 0V9, Canada; and.
authors.forename: Spencer B
authors.identifier: http://orcid.org/0000-0003-0119-732X
authors.initials: SB
authors.lastname: Gibson
authors.affiliation: Department of Immunology, University of Manitoba, Winnipeg, Manitoba R3E 0T5, Canada; Department of Physics and Astronomy, University of Manitoba, Winnipeg, Manitoba R3T 2N2, Canada.
authors.forename: Francis
authors.initials: F
authors.lastname: Lin
authors.affiliation: Department of Immunology, University of Manitoba, Winnipeg, Manitoba R3E 0T5, Canada; Department of Biochemistry and Medical Genetics, University of Manitoba, Winnipeg, Manitoba R3E 0T5, Canada; Research Institute in Oncology and Hematology, Winnipeg, Manitoba R3E 0V9, Canada; and aaron.marshall@umanitoba.ca.
authors.forename: Aaron J
authors.identifier: http://orcid.org/0000-0002-1175-5498
authors.initials: AJ
authors.lastname: Marshall
mesh_terms: D015153:Blotting, Western; D002352:Carrier Proteins / Q000378:metabolism*; D045744:Cell Line, Tumor; D002634:Chemotaxis, Leukocyte / Q000502:physiology*; D005434:Flow Cytometry; D006801:Humans; D015451:Leukemia, Lymphocytic, Chronic, B-Cell / Q000378:metabolism / Q000473:pathology*; D013058:Mass Spectrometry; D008565:Membrane Proteins / Q000378:metabolism*; D018613:Microscopy, Confocal; D010744:Phosphoric Monoester Hydrolases / Q000378:metabolism*; D014162:Transfection
chemical_list: D002352:Carrier Proteins; D008565:Membrane Proteins; C493339:RAPH1 protein, human; D010744:Phosphoric Monoester Hydrolases; C053153:phosphatidylinositol-3,4-bisphosphate 4-phosphatase