Quantitative Motion-Corrected PALM Links Endosome Structure and Dynamics in Live Cells

Abstract

Quantitative structural analysis by Photoactivated Localization Microscopy (PALM) on the nanoscale is often restricted to fixed cells because motion during prolonged data acquisition distorts image reconstruction. Here, we develop motion-corrected PALM (mcPALM), a live-cell super-resolution approach combining a conventional fluorescence channel with PALM to correct motion-induced spreading of localizations. We further introduce a photoactivation-based correction to estimate molecule numbers from incomplete trajectories. Using PI3P-marked endosomes in yeast as a dynamic model system, we show that mcPALM recovers a live-cell maturation trajectory linking motion-corrected endosome size and calibrated PI3P content, consistent with fixed-cell benchmarks. Unlike fixed-cell PALM, mcPALM preserves endosome dynamics, revealing stage-dependent directed transport and maturation-associated motility shift. Thus, mcPALM extends PALM from static structural measurements in fixed samples to integrated quantification of nanoscale structure, molecular composition and dynamics in living cells. This framework is broadly applicable to other mobile organelles and biomolecular assemblies, enabling live-cell studies on how molecular organization and dynamics are coupled to biological function.