Cells rely on a highly organized transport system to move essential materials, such as proteins, organelles, and signaling molecules, to precise locations. This process is especially critical in neurons, where cargo must travel long distances to maintain proper function and survival. Failures in intracellular transport are linked to major neurological disorders, including Alzheimer’s and Parkinson’s diseases. Although molecular motors such as kinesin are responsible for carrying cargo along cellular “tracks” called microtubules, it remains unclear how these motors are selectively regulated to ensure accurate delivery. Emerging evidence suggests that proteins decorating microtubules, known as microtubule-associated proteins (MAPs), act as key regulators that determine which motors can access and move along these tracks. However, the mechanisms by which MAPs selectively activate or inhibit different motors are poorly understood. This project aims to uncover how MAPs control motor-driven transport at the molecular level. By revealing fundamental principles governing intracellular transport, this work will advance understanding of cellular organization and the molecular basis of neurological disease. The project also contributes to national priorities by supporting STEM education and workforce development, including the engagement of high school students in research activities and the integration of interdisciplinary training in physics and biology at the undergraduate level. This project will combine structural biology, biophysics, and protein engineering to determine how specific MAPs (tau, MAP7, MAP9, and doublecortin) regulate the activity of kinesin-1 and kinesin-3 motors. The research will pursue four main objectives. First, it will determine the full structural footprint of MAPs on microtubules using cryo-electron microscopy (cryo-EM) and newly developed labeling strategies that overcome current resolution limitations. Second, it will define how tau inhibits m