Dong Li1,2,5, Hui Tu1,3,5 and Huaqing Cai1,4 1National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China 2Department of Cell Biology, School of Medicine, Johns Hopkins University, Baltimore, Maryland 21205, USA 3Institute of Systems Biomedicine, Beijing Key Laboratory of Tumor Systems Biology, School of Basic Medical Sciences, Peking University Health Science Center, Peking University, Beijing 100191, China 4College of Life Sciences, University of Chinese Academy of Sciences, Beijing 100049, China Correspondence: huaqingcaiibp.ac.cn

↵5 These authors contributed equally to this work.

Cell migration plays a central role in a wide range of physiological, developmental, and disease-related processes. Studies using single-cell models, such as Dictyostelium discoideum, have provided important insights into the molecular principles underlying this process. Migrating cells exhibit a polarized morphology, with actin-rich protrusions at the leading edge driving forward motion and an actomyosin network at the trailing edge enabling retraction. While actin polymerization and direct cytoskeletal regulators are essential, a complex network of signaling molecules also play a critical role in cell migration. Initially viewed as part of the directional sensing machinery in guided migration, this signaling network is now also recognized as an integral component of the motility module itself. Its spontaneous activity coordinates with cytoskeletal reorganization, enabling cell migration even in the absence of external cues. This review highlights key cytoskeletal and signaling molecules involved in leading-edge protrusion formation, with an emphasis on findings from Dictyostelium studies. We also discuss recent advances in understanding how these cytoskeletal and signaling molecules organize into excitable networks to regulate cell motility.