COVER: Endoplasmic reticulum (ER) localization of the kinase negative (KN) form of lemur kinase 1B (LMTK1B) in a CHO-K1 cell. LMTK1 is an uncharacterized Ser/Thr protein kinase, expressed mainly in neurons. There are two isoforms of LMTK1, LMTK1A and LMTK1B. The cytosolic LMTK1A binds to membranes through palmitoylation, whereas LMTK1B is an integral membrane protein. It is recently shown that LMTK1A regulates axon outgrowth, dendrite arborization and spine formation via the regulation of Rab11-dependent recycling endosome trafficking, but almost nothing was known about LMTK1B. We investigated the cellular localization and function of LMTK1B (Wei et al., in this issue). When LMTK1B was expressed in CHO-K1 cells, while wild type LMTK1B localized to the pericentrosomal endocytic recycling compartment, LMTK1B KN showed localization to the tubular ER stained with a KDEL ER maker.

Structured illumination microscope (SIM) images of LMTK1B KN (left), ER (middle) and the merge (right) are shown. Bar, 5 mm.

Wei R., Sugiyama A., Sato Y., Nozumi M., Nishino H., Takahashi M., Saito T., Ando K., Fukuda M., Tomomura M., Igarashi M., Hisanaga S. (2020) Isoform-dependent subcellular localization of LMTK1A and LMTK1B and their roles in axon outgrowth and spine formation. J. Biochem. 168, 23–32