Tracking of single microvilli to study regulation of the intestinal phosphate transporters

Abstract

Intestinal phosphate (Pi) uptake is a key mechanism in systemic Pi homeostasis. Modulation of intestinal Pi transport has been recently recognized as an important target in prevention of hyperphosphatemia and the associated cardiovascular complications in Chronic Kidney Disease. Intestinal Pi absorption is mainly mediated by the sodium‐phosphate co‐transporter NaPi2b expressed in the intestinal apical microvilli. Recent evidences show that agonists of the LXR nuclear hormone receptor inhibit intestinal NaPi transport activity, however, the detailed mechanisms of how LXR decreases intestinal NaPi transport activity, including the role of changes in membrane cholesterol or PDZ interacting proteins, remain to be determined.We study these processes at the molecular level applying the Modulation Tracking nanoimaging method to microvilli of live cells expressing fluorescently tagged NaPi2b. Tracking single microvilli we measure their motion, image NaPi2b distribution on the membrane and perform Fluorescence Correlation Spectroscopy techniques (RICS, N&B) in steady state, even if the microvilli are moving. Motility of the microvilli, protein diffusion and clustering, are monitored under stimulation to get insights into the process of intestinal transporters regulation.Work supported in part by NIH R01 DK066029‐01A2 (ML, EG and LL), NIH‐P41‐RR03155 (EG and LL) and P50‐GM076516 (EG, MD and LL).