ROCK1 via LIM kinase regulates growth, maturation and actin based functions in mast cells

// Reuben Kapur 1, 2 , Jianjian Shi 1 , Joydeep Ghosh 2 , Veerendra Munugalavadla 3 , Emily Sims 1 , Holly Martin 1 , Lei Wei 1 , Raghuveer Singh Mali 1 1 Department of Pediatrics, Herman B Wells Center for Pediatric Research, Indiana University School of Medicine, Indianapolis, IN, USA 2 Department of Microbiology and Immunology, Indiana University School of Medicine, Indianapolis, IN, USA 3 Gilead Sciences, Inc., Foster City, CA, USA Correspondence to: Raghuveer Singh Mali, e-mail: rsmali@iupui.edu Keywords: mast cells, Rho kinase, LIM kinase, cell growth, anaphylaxis Received: October 21, 2015 Accepted: January 29, 2016 Published: March 02, 2016 ABSTRACT Understanding mast cell development is essential due to their critical role in regulating immunity and autoimmune diseases. Here, we show how Rho kinases (ROCK) regulate mast cell development and can function as therapeutic targets for treating allergic diseases. Rock1 deficiency results in delayed maturation of bone marrow derived mast cells (BMMCs) in response to IL-3 stimulation and reduced growth in response to stem cell factor (SCF) stimulation. Further, integrin-mediated adhesion and migration, and IgE-mediated degranulation are all impaired in Rock1-deficient BMMCs. To understand the mechanism behind altered mast cell development in Rock1−/− BMMCs, we analyzed the activation of ROCK and its downstream targets including LIM kinase (LIMK). We observed reduced activation of ROCK, LIMK, AKT and ERK1/2 in Rock1-deficient BMMCs in response to SCF stimulation. Further, loss of either Limk1 or Limk2 also demonstrated altered BMMC maturation and growth; combined deletion of both Limk1 and Limk2 resulted in further reduction in BMMC maturation and growth. In passive cutaneous anaphylaxis model, deficiency of Rock1 or treatment with ROCK inhibitor Fasudil protected mice against IgE-mediated challenge. Our results identify ROCK/LIMK pathway as a novel therapeutic target for treating allergic diseases involving mast cells.