Class IA PI3Kinase Regulatory Subunit, p85α, Mediates Mast Cell Development through Regulation of Growth and Survival Related Genes

Subha Krishnan,Raghuveer Singh Mali,Karl R Koehler,Sasidhar Vemula,Joydeep Ghosh,Baskar Ramdas,Peilin Ma,Reuben Kapur,Anindya Chatterjee,Eri Hashino,Cheng-Kui Qu

doi:10.1371/journal.pone.0028979

Abstract

Stem cell factor (SCF) mediated KIT receptor activation plays a pivotal role in mast cell growth, maturation and survival. However, the signaling events downstream from KIT are poorly understood. Mast cells express multiple regulatory subunits of class 1A PI3Kinase (PI3K) including p85α, p85β, p50α, and p55α. While it is known that PI3K plays an essential role in mast cells; the precise mechanism by which these regulatory subunits impact specific mast cell functions including growth, survival and cycling are not known. We show that loss of p85α impairs the growth, survival and cycling of mast cell progenitors (MCp). To delineate the molecular mechanism (s) by which p85α regulates mast cell growth, survival and cycling, we performed microarray analyses to compare the gene expression profile of MCps derived from WT and p85α-deficient mice in response to SCF stimulation. We identified 151 unique genes exhibiting altered expression in p85α-deficient cells in response to SCF stimulation compared to WT cells. Functional categorization based on DAVID bioinformatics tool and Ingenuity Pathway Analysis (IPA) software relates the altered genes due to lack of p85α to transcription, cell cycle, cell survival, cell adhesion, cell differentiation, and signal transduction. Our results suggest that p85α is involved in mast cell development through regulation of expression of growth, survival and cell cycle related genes.

Highlights

Mast cells are critical mediators of inflammation, innate immunity and host defense that originate from multipotent stem cells in the bone marrow (BM) [1]
To assess the contribution of p85a in mast cell growth, bone marrow–derived mast cells (BMMC) from WT and p85a2/2 mice were subjected to proliferation assay in the presence or absence of Stem cell factor (SCF)
While WT BMMCs demonstrated a significant increase in growth in the presence of SCF, deficiency of p85a resulted in complete loss of SCF mediated growth (Figure 1)

Summary

Introduction

Mast cells are critical mediators of inflammation, innate immunity and host defense that originate from multipotent stem cells in the bone marrow (BM) [1]. While several cytokines influence the growth, survival and maturation of mast cells, SCF and its interaction with KIT receptor are critical for normal mast cell development and function. The intracellular signals downstream from KIT in regulating both growth and survival of mast cells are poorly understood. Recent studies have shown that PI3Kinase (PI3K), which binds to tyrosine at position 719 in murine KIT (at 721 in human KIT) through its regulatory subunit contributes substantially to KIT mediated mast cell functions [9,10]. Utilizing genetic and genomic approaches, we evaluate the role of p85a in mast cell development and functions in response to SCF stimulation. We provide evidence for the critical role of p85a in mast cell growth, survival and cycling; and possible pathways by which p85a regulates mast cell functions in response to SCF stimulation

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Results

Conclusion