The role of calpain isoforms in regulating neutrophil migration

• Main Author: Nuzzi, Paul A
• Format: Dissertation
• Language: English
• Published: ProQuest Dissertations & Theses 01-01-2006
• Subjects: Cellular biology; Immunology; Pharmacology
• ISBN: 0542753316; 9780542753312

Cell migration is a dynamic and complex process required for countless biological processes such as embryonic development, wound healing, tissue repair and immune surveillance. At its most elemental level, cell migration can be thought of as a cyclic process involving cell adhesion at the front, contraction in the center and release of the cell rear for forward translocation. However, it is the way these events are regulated within each cell that determines the way in which the cell migrates. This is especially true for neutrophils, which constitute the bulk of the innate immune response, policing the body for infection using a specialized form of chemotactic migration. The calpain family of calcium-dependent intracellular proteases, have been previously shown to play an important role in regulating fibroblast migration. This dissertation examines the role of calpain 1 and 2 isoforms in regulating neutrophil migration. The research presented in chapter 2 characterizes a role for the calpain 1 isoform in regulating neutrophil protrusion. Inhibition of calpain 1 activity stimulated random neutrophil migration in an absence of chemoattractant stimulation. These cells display an increase in cell protrusion and migration speed, similar to that of IL-8 or fMLP. Calpain 1 was found to function down-stream of GPCRs and regulate protrusion through Cdc42 and Rac. These findings suggest that calpain 1 may function as a negative regulator of protrusion in neutrophils. Chapter 3 characterizes the role of calpain 2 in neutrophil migration and suggests that calpain 2 may be critical in regulating neutrophil chemotaxis. Immunofluorescent staining and biochemical studies revealed that calpain 1 and 2 are asymmetrically localized during chemotaxis. Calpain 2 was found to translocate to the leading edge early in pseudopod formation and is important for establishing neutrophil polarity. This translocation occurs in an actin-dependent process and utilizes lipid rafts domains at the leading edge of the cell. Together, the research described in this dissertation provides a novel role for calpain in neutrophil migration. Furthermore, it characterizes a unique role for calpain 1 and 2 in neutrophil migration and emphasizes the importance of asymmetry during chemotactic migration.