Wiskott-Aldrich syndrome protein is an effector of Kit signaling.
The pleiotropic receptor tyrosine kinase Kit can provide cytoskeletal signals that define cell shape, positioning, and migration, but the underlying mechanisms are less well understood. In this study, we provide evidence that Kit signals through Wiskott-Aldrich syndrome protein (WASP), the central hematopoietic actin nucleation-promoting factor and regulator of the cytoskeleton. Kit ligand (KL) stimulation resulted in transient tyrosine phosphorylation of WASP, as well as interacting proteins WASP-interacting protein and Arp2/3. KL-induced filopodia in bone marrow-derived mast cells (BMMCs) were significantly decreased in number and size in the absence of WASP. KL-dependent regulation of intracellular Ca(2+) levels was aberrant in WASP-deficient BMMCs. When BMMCs were derived from WASP-heterozygous female mice using KL as a growth factor, the cultures eventually developed from a mixture of WASP-positive and -negative populations into a homogenous WASP-positive culture derived from the WASP-positive progenitors. Thus, WASP expression conferred a selective advantage to the development of Kit-dependent hematopoiesis consistent with the selective advantage of WASP-positive hematopoietic cells observed in WAS-heterozygous female humans. Finally, KL-mediated gene expression in wild-type and WASP-deficient BMMCs was compared and revealed that approximately 30% of all Kit-induced changes were WASP dependent. The results indicate that Kit signaling through WASP is necessary for normal Kit-mediated filopodia formation, cell survival, and gene expression, and provide new insight into the mechanism in which WASP exerts a strong selective pressure in hematopoiesis.
Mani
Maheswaran
M
Division of Stem Cell Transplantation, Department of Pediatrics, Stanford University School of Medicine, CA 94305-5208, USA.
Venkatasubrahmanyam
Shivkumar
S
Sanyal
Mrinmoy
M
Levy
Shoshana
S
Butte
Atul
A
Weinberg
Kenneth
K
Jahn
Thomas
T
D051377:Actin-Related Protein 2 / Q000378:metabolism; D000818:Animals; D001853:Bone Marrow / Q000378:metabolism; D002118:Calcium / Q000378:metabolism; D002352:Carrier Proteins / Q000378:metabolism; D003598:Cytoskeletal Proteins; D005260:Female; D005434:Flow Cytometry; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation; D015151:Immunoblotting; D047468:Immunoprecipitation; D008407:Mast Cells / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D020411:Oligonucleotide Array Sequence Analysis; D010766:Phosphorylation; D019009:Proto-Oncogene Proteins c-kit / Q000378:metabolism*; D011554:Pseudopodia / Q000378:metabolism; D015398:Signal Transduction; D019089:Stem Cell Factor / Q000378:metabolism*; D014443:Tyrosine / Q000378:metabolism; D051316:Wiskott-Aldrich Syndrome Protein / Q000502:physiology*
D051377:Actin-Related Protein 2; D002352:Carrier Proteins; D003598:Cytoskeletal Proteins; D019089:Stem Cell Factor; C495768:Was protein, mouse; C491671:Waspip protein, mouse; D051316:Wiskott-Aldrich Syndrome Protein; D014443:Tyrosine; D019009:Proto-Oncogene Proteins c-kit; D002118:Calcium