Neurospora crassa NKIN2, a Kinesin-3 Motor, Transports Early Endosomes and Is Required for Polarized Growth

Seidel, Constanze; Moreno-Velásquez, Sergio D.; Riquelme, Meritxell; Fischer, Reinhard

doi:10.1128/ec.00081-13

Cited by 39 publications

(50 citation statements)

References 47 publications

(71 reference statements)

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“…S2A and S2B in the supplemental material). Two orthologs of Rab-5 have been identified in N. crassa (52). These orthologs are predicted to associate with vesicles that carry proteins between endosomes and the plasma membrane.…”

Section: Resultsmentioning

confidence: 99%

Characterization of a Novel Prevacuolar Compartment in Neurospora crassa

et al. 2015

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Using confocal microscopy, we observed ring-like organelles, similar in size to nuclei, in the hyphal tip of the filamentous fungus Neurospora crassa. These organelles contained a subset of vacuolar proteins. We hypothesize that they are novel prevacuolar compartments (PVCs). We examined the locations of several vacuolar enzymes and of fluorescent compounds that target the vacuole. Vacuolar membrane proteins, such as the vacuolar ATPase (VMA-1) and the polyphosphate polymerase (VTC-4), were observed in the PVCs. A pigment produced by adenine auxotrophs, used to visualize vacuoles, also accumulated in PVCs. Soluble enzymes of the vacuolar lumen, alkaline phosphatase and carboxypeptidase Y, were not observed in PVCs. The fluorescent molecule Oregon Green 488 carboxylic acid diacetate, succinimidyl ester (carboxy-DFFDA) accumulated in vacuoles and in a subset of PVCs, suggesting maturation of PVCs from the tip to distal regions. Three of the nine Rab GTPases in N. crassa, RAB-2, RAB-4, and RAB-7, localized to the PVCs. RAB-2 and RAB-4, which have similar amino acid sequences, are present in filamentous fungi but not in yeasts, and no function has previously been reported for these Rab GTPases in fungi. PVCs are highly pleomorphic, producing tubular projections that subsequently become detached. Dynein and dynactin formed globular clusters enclosed inside the lumen of PVCs. The size, structure, dynamic behavior, and protein composition of the PVCs appear to be significantly different from those of the well-studied prevacuolar compartment of yeasts.T he vacuolar compartments in cells of fungi and plants have many of the same functions as the lysosomal compartments of animal cells (1-5). The defining characteristics of vacuoles and lysosomes are (i) the presence of a variety of hydrolytic enzymes such as proteases and phosphatases that help to degrade and recycle macromolecules and (ii) the maintenance of an acidic internal pH. An electrochemical gradient for protons is generated across vacuolar/lysosomal membranes by the vacuolar ATPase, a large complex enzyme (1, 6).We have been investigating the structure and function of the vacuolar compartments in filamentous fungi, using Neurospora crassa as our model organism. In fungi, vacuoles have multiple functions in addition to the degradation of macromolecules. They are involved in the regulation of arginine and ornithine metabolism, osmoregulation, and cytosolic ion and pH homeostasis. Fungal vacuoles contain high concentrations of basic amino acids, calcium, and polyphosphate (1, 4, 5).The vacuolar compartment in filamentous fungi has a complex structure and is highly dynamic (3,7,8). Many vacuoles have internal contents with a different refractive index than that of the cytosol, allowing them to be visualized with Nomarski optics. These vacuoles, prominent in older parts of the hypha, are spherical, ranging in size from Ͻ0.5 m to Ͼ10 m. Other vacuoles, prominent in the first hyphal segment, take the form of a dense network of interconnected tubules (9, 10). For N. cra...

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Section: Resultsmentioning

confidence: 99%

Characterization of a Novel Prevacuolar Compartment in Neurospora crassa

et al. 2015

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“…KIF16B transports Rab5 positive early endosomes and Rab14 positive vesicles in non neuronal cells [31,66]. Also, the Neurospora kinesin 3 NKin2 colocalizes with the Rab5 GTPase YPT52 [8]. DmKlp98A interacts with Rab14 and Atg8 (autophagic vesicle associated protein).…”

Section: Regulation By Rab Gtpasesmentioning

confidence: 99%

“…The fungal kinesin 3 UncA from A. nidulans has been reported to selectively walk on detyrosinated microtubules, and the tail is necessary and sufficient for this recognition [9,106]. Also, the N. crassa kinesin 3 NKin2 preferentially binds to a subset of microtubules [8]. However, this feature is not conserved in all fungi, as Kin3 from U. maydis uses all microtubules equally [107].…”

Section: Specificity For a Subset Of Microtubule Tracksmentioning

confidence: 99%

Intracellular cargo transport by kinesin-3 motors

Siddiqui

Straube

2017

Biochemistry Moscow

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Abstract-Intracellular transport along microtubules enables cellular cargoes to efficiently reach the extremities of large, eukaryotic cells. While it would take more than 200 years for a small vesicle to diffuse from the cell body to the growing tip of a one meter long axon, transport by a kinesin allows delivery in one week. It is clear from this example that the evolution of intracellular transport was tightly linked to the development of complex and macroscopic life forms. The human genome encodes 45 kinesins, 8 of those belonging to the family of kinesin 3 organelle transporters that are known to transport a vari ety of cargoes towards the plus end of microtubules. However, their mode of action, their tertiary structure, and regulation are controversial. In this review, we summarize the latest developments in our understanding of these fascinating molecular motors.

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“…3G). UncA is involved in early endosome movement (15,26). These results suggest that only a fraction of RcyA is transported along microtubules on early endosomes.…”

Section: Resultsmentioning

confidence: 87%

“…In addition, subapical endocytosis is required for recycling of excess membrane and membrane-bound proteins (12)(13)(14)(15). The direction of vesicle flow is strictly regulated through the orientation and polarization of the microtubule and the actin cytoskeletons.…”

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F-Box Protein RcyA Controls Turnover of the Kinesin-7 Motor KipA in Aspergillus nidulans

2014

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bFungal filamentous growth depends on continuous membrane insertion at the tip, the delivery of membrane-bound positional markers, and the secretion of enzymes for cell wall biosynthesis. This is achieved through exocytosis. At the same time, polarized growth requires membrane and protein recycling through endocytosis. Endocytic vesicles are thought to enter the protein degradation pathway or recycle their content to the cell surface. In Saccharomyces cerevisiae, the Rcy1 F-box protein is involved in the recycling process of a v-SNARE protein. We identified a Rcy1 orthologue, RcyA, in the filamentous fungus Aspergillus nidulans as a protein interacting with the KipA kinesin-7 motor protein in a yeast two-hybrid screen. The interaction was confirmed through bimolecular fluorescence complementation. RcyA possesses an F-box domain at the N terminus and a prenylation (CaaX) motif at the C terminus. RcyA shows also similarity to Sec10, a component of the exocyst complex. The RcyA protein localized to the hyphal tip and forming septa, likely through transportation on secretory vesicles and partially on early endosomes, but independently of KipA. Deletion of rcyA did not cause severe morphological changes but caused partial defects in the recycling of the SynA v-SNARE protein and the positioning of the cell end markers TeaA and TeaR. In addition, deletion of rcyA led to increased concentrations of the KipA protein, whereas the transcript concentration was unaffected. These results suggest that RcyA probably labels KipA for degradation and thereby controls the protein amount of KipA.

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Neurospora crassa NKIN2, a Kinesin-3 Motor, Transports Early Endosomes and Is Required for Polarized Growth

Cited by 39 publications

References 47 publications

Characterization of a Novel Prevacuolar Compartment in Neurospora crassa

Characterization of a Novel Prevacuolar Compartment in Neurospora crassa

Intracellular cargo transport by kinesin-3 motors

F-Box Protein RcyA Controls Turnover of the Kinesin-7 Motor KipA in Aspergillus nidulans

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