Optineurin Localization at the Centrosome, Spindle, and Midbody Implies Its Role in Cell Division.

Optineurin (OPTN), a multifunctional cytosolic protein, is recognized as an autophagy adaptor. Its association with neurodegenerative diseases, like ALS, triggered extensive research. OPTN has been found in intracellular organelles, including the mitochondria, Golgi body, endosomes, microtubules, and the nucleus. The report of mitotic defects and delayed cell division in OPTN-depleted cells prompted us to explore OPTN's exact localization in the cell that could interfere with cell division assemblies. We used three distinct human cell lines, HeLa, HEK293, and SH-SY5Y, and probed them for OPTN localization using both centrosomal (Aurora A kinase, pericentrin, PCM1, Cep170, and γ-tubulin) and mitotic spindle markers (β-tubulin). Our immunofluorescence-based detection using wide-field fluorescence, confocal, and structured illumination microscopy (SIM) placed OPTN at the centrosome, which remained associated with the centriole after duplication and their migration during mitosis. OPTN was also observed at the junction of daughter cells during cytokinesis. Our finding reveals unmapped localizations of OPTN with key cytosolic assemblies that are directly involved in cell division.