title: Neurospora crassa NKIN2, a kinesin-3 motor, transports early endosomes and is required for polarized growth.
abstract: Biological motors are molecular nanomachines, which convert chemical energy into mechanical forces. The combination of mechanoenzymes with structural components, such as the cytoskeleton, enables eukaryotic cells to overcome entropy, generate molecular gradients, and establish polarity. Hyphae of filamentous fungi are among the most polarized cells, and polarity defects are most obvious. Here, we studied the role of the kinesin-3 motor, NKIN2, in Neurospora crassa. We found that NKIN2 localizes as fast-moving spots in the cytoplasm of mature hyphae. To test whether the spots represented early endosomes, the Rab5 GTPase YPT52 was used as an endosomal marker. NKIN2 colocalized with YPT52. Deletion of nkin2 caused strongly reduced endosomal movement. Combined, these results confirm the involvement of NKIN2 in early endosome transport. Introduction of a rigor mutation into NKIN2 labeled with green fluorescent protein (GFP) resulted in decoration of microtubules. Interestingly, NKIN2(rigor) was associated with a subpopulation of microtubules, as had been shown earlier for the Aspergillus nidulans orthologue UncA. Other kinesins did not show this specificity.
authors.affiliation: Karlsruhe Institute of Technology-South Campus, Institute for Applied Biosciences, Department of Microbiology, Karlsruhe, Germany.
authors.forename: Constanze
authors.initials: C
authors.lastname: Seidel
authors.forename: Sergio David
authors.initials: SD
authors.lastname: Moreno-Velásquez
authors.forename: Meritxell
authors.initials: M
authors.lastname: Riquelme
authors.forename: Reinhard
authors.initials: R
authors.lastname: Fischer
mesh_terms: D001692:Biological Transport; D016764:Cell Polarity; D011992:Endosomes / Q000378:metabolism*; D005656:Fungal Proteins / Q000737:chemistry / Q000378:metabolism; D017353:Gene Deletion; D049452:Green Fluorescent Proteins / Q000378:metabolism; D025301:Hyphae / Q000254:growth & development / Q000378:metabolism; D016547:Kinesins / Q000737:chemistry / Q000378:metabolism*; D008870:Microtubules / Q000378:metabolism; D009068:Movement; D009492:Neurospora crassa / Q000166:cytology / Q000254:growth & development* / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D011993:Recombinant Fusion Proteins / Q000378:metabolism
chemical_list: D005656:Fungal Proteins; D011993:Recombinant Fusion Proteins; D049452:Green Fluorescent Proteins; D016547:Kinesins