MARK4 is a serine/threonine protein kinase that primarily regulates microtubule dynamics and cellular organization 1. The kinase phosphorylates microtubule-associated proteins including tau/MAPT, MAP2, and MAP4, promoting microtubule bundling and reorganization 12. MARK4 is essential for cilium assembly, mediating axoneme extension initiation and controlling ODF2 centrosomal localization 3. Beyond cytoskeletal functions, MARK4 regulates cell cycle progression at the G1/S checkpoint 4 and acts as a negative regulator of mTORC1 signaling by phosphorylating RPTOR 5. The kinase also coordinates NLRP3 inflammasome positioning at microtubule organizing centers 6. Disease relevance is substantial. In Alzheimer's disease, MARK4-mediated tau hyperphosphorylation contributes to neurofibrillary tangle formation and neuronal vulnerability 78. MARK4 knockdown or inhibition ameliorates tau pathology and rescues memory deficits in AD models 8. Elevated MARK4 expression is associated with impaired cardiac contractility in heart failure patients, correlating with reduced ejection fraction and diastolic dysfunction 9. MARK4 also promotes cancer cell proliferation in breast and lung cancers 1011, making it a therapeutic target. Additionally, MARK4 interacts with mitofusin-2 to regulate mitochondrial fusion and synaptic integrity 12. These findings position MARK4 as a clinically relevant drug target across neurodegenerative, cardiovascular, and malignant diseases.