BPS2026 – Mechanisms controlling SHIP1 localization and dynamics during neutrophil chemotaxis

Neutrophils are the frontline defenders of our immune system. These white blood cells deploy to sites of infection by detecting chemical gradients, polarizing, and migrating toward foreign pathogens. This process, known as chemotaxis, requires communication between small GTPases, phosphatidylinositol phosphate (PIP) lipids, and the actin cytoskeleton to generate forces that drive membrane protrusions. Central to the coordination of these biochemical reactions, is the hematopoietic-cell-specific lipid phosphatase denoted SHIP1 (or INPP5D). Critical for chemotaxis, this lipid phosphatase regulates the dephosphorylation of phosphatidylinositol-(3,4,5)-trisphosphate lipids to generate PI(3,4)P 2 . The mechanisms by which SHIP1 and associated proteins orchestrate cytoskeletal dynamics to drive chemotaxis, however, remain poorly understood. Beyond its catalytic activity, SHIP1 is predicted to scaffold proteins for recruitment to the plasma membrane. To decipher mechanisms of SHIP1 regulation, we combined genetic manipulation of SHIP1 in neutrophil-like cells with high-resolution imaging and computational analysis. Using a photoactivatable bacterial peptide to generate chemoattract gradients, we quantified the chemotactic phenotypes of SHIP1 knockdowns, rescues, and domain-specific mutants. Chemotaxis was quantified using machine learning-based segmentation and custom MATLAB workflows. In parallel, we used total internal reflection fluorescence (TIRF) microscopy to visualize the dynamics of plasma membrane localized SHIP1. Our results reveal two distinct modes of SHIP1 localization: (1) cortical oscillations that propagate in concert with the cell polarity factor Cdc42 GTPase and F-BAR protein FBP17 and (2) dynamic puncta that accumulate into condensates mediated by the adapter protein Nck1. This work reveals a dual mechanism by which SHIP1 integrates membrane signaling and the actin cytoskeleton to control immune cell migration.