Use they’re capable to separate the two daughter nuclei solely by pulling forces exerted through astral microtubules, most like by means of minus-end directed motor activity of cortical dynein [237]. 4. Centrosome-Nucleus Attachment Like all centrosomal structures in vegetative cells, the Dictyostelium centrosome is structurally linked for the cytosolic side on the nucleus Sutezolid site throughout interphase. Not surprisingly, a single essential protein of this linkage may be the nuclear envelope protein Sun1, named right after the founding members from the Sun-family, i.e., fission yeast Sad1 and Caenorhabditis elegans UNC-84, which share a popular Sun-domain. In most eukaryotes Sun1 is definitely an inner nuclear membrane protein, forming a trimer and interacting, by means of its Phenylacetylglutamine Epigenetics Sun-domain, with the so-called KASH-domain proteins (named right after Klarsicht, ANC-1, SYNE1 homology) within the perinuclear space [239]. Since the various KASH domain proteins interact directly or indirectly with all 3 cytoskeletal components (actin, microtubules, intermediate filaments) the term LINC complex (linker in the nucleus and cytoskeleton) was coined for the Sun/KASH domain protein heterodimer [240]. In the nuclear side, Sun1 interacts with lamins in animal cells as well as in Dictyostelium [241]. Yet, on the cytosolic face of your nuclear envelope the situation in Dictyostelium seems to be distinctive. Sun1 is present in each nuclear membanes with no sturdy bias towards the inner nuclear membrane [124,125] and there is no clear orthologue for a KASH domain protein. As a result of its similarity to mammalian nesprins, the outer nuclear membrane protein interaptin was discussed as a Dictyostelium KASH domain protein [125,242]. But interaptin is definitely no aspect of a LINC complex, because it lacks the conserved KASH domain and of course does not interact with Sun1 [125]. Sun1 is however expected for centrosome/nucleus attachment. It co-purifies with isolated centrosomes and is concentrated in the nuclear envelope inside the direct vicinity with the centrosome (Figure four). Sun1 mutants are defective in centrosome/nucleus attachment. It can be attainable that the centrosome/nucleus linker employs Sun1 on both sides on the membrane, and that an unknown protein of the perinuclear space mediates this interaction. Even though a direct interaction with Sun1 remains to be verified, the uncommon kinesin Kif9 is often a most likely candidate for a LINC complex component in Dictyostelium. Kif9 is definitely an internal motor kinesin, which might be grouped in to the kinesin-13 family, which normally act as microtubule depolymerases [130]. Inside this group Kif9 is one of a kind in containing a 23 residue transmembrane domain close to its C-terminal end, targeting the protein towards the outer nuclear envelope exactly where it accumulates within the pericentrosomal region. Knockout of Kif9 disrupts the centrosome/nucleus linkage and causes dispersal of Sun1, away in the pericentrosomal region from the nuclear envelope [130].Figure four. Centrosome-Nucleus-Centromere cluster. (A) Immunoelectron microscopy image showing a single section of an isolated nucleus using the attached centrosome. Nuclei had been labeled with an antibody against Dictyostelium Sun1 and nanogold conjugated anti-rabbit antibodies. The centrosome (Cn), the centromeric cluster (Cm), the nuclear envelope (NE) and the endoplasmic reticulum (ER) are indicated (image by Prof. Otto Baumann); (B) Immunofluorescence microscopy image of a Sun1-GFP knock-in cell (green) stained with an antibody against the centrosomal core protein CP91 and anti-rabbit-AlexaFluor 568 conjug.