Summary Background Formation of epithelial sheets requires that cell division occurs in the plane of the sheet. During mitosis, spindle poles align so the astral microtubules contact the lateral cortex. Confinement of the mammalian Pins protein to the lateral cortex is essential for this process. Defects in signaling through Cdc42 and atypical protein kinase C (aPKC) also cause spindle misorientation. When epithelial cysts are grown in 3D cultures, mis-orientation creates multiple lumens. Results We now show that silencing of the polarity protein Par3 causes spindle mis-orientation in MDCK cell cysts. Silencing of Par3 also disrupts aPKC association with the apical cortex, but expression of an apically-tethered aPKC rescues normal lumen formation. During mitosis, Pins is mislocalized to the apical surface in the absence of Par3, or by inhibition of aPKC. Active aPKC increases Pins phosphorylation on Ser401, which recruits 14-3-3 protein. 14-3-3 binding inhibits association of Pins with Gαi, through which Pins attaches to the cortex. A Pins S401A mutant mislocalizes over the cell cortex and causes spindle orientation and lumen defects. Conclusions The Par3/aPKC polarity proteins ensure correct spindle pole orientation during epithelial cell division by excluding Pins from the apical cortex. Apical aPKC phosphorylates Pins, which results in the recruitment of 14-3-3 and inhibition of binding to Gαi, so the Pins falls off the cortex. In the absence of a functional exclusion mechanism, astral microtubules can associate with Pins over the entire epithelial cortex, resulting in randomized spindle pole orientation.

Abbreviations used in this paper: aPKC, atypical protein kinase C; Crb3, Crumbs3; G, the alpha subunit of the heterotrimeric G proteins; Gi, the alpha subunit of adenylyl cyclase-inhibitory heterotrimeric G proteins; GoLoco motif, G i/o -Loco motif; LGN, mammalian homologue of Pins; MT, microtubule; NuMA, nuclear mitotic apparatus protein; Pins, partner of inscuteable.

Despite the longer operative time, LA results in less postoperative pain, faster postoperative rehabilitation, a shorter hospital stay, and fewer postoperative complications than OA. Therefore, LA is worth recommending as an effective and safe procedure for acute appendicitis.

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Summary Asymmetric cell division requires the establishment of cortical cell polarity and the orientation of the mitotic spindle along the axis of cell polarity. Evidence from invertebrates demonstrates that the Par3/Par6/aPKC and NuMA/LGN/Gαi complexes, which are thought to be physically linked by the adapter protein mInscuteable (mInsc), play indispensable roles in this process. However, the molecular basis for the binding of LGN to NuMA and mInsc is poorly understood. The high resolution structures of the LGN/NuMA and LGN/mInsc complexes presented here provide mechanistic insights into the distinct and highly specific interactions of the LGN TPR repeats with mInsc and NuMA. Structural comparisons, together with biochemical and cell biology studies, demonstrate that the interactions of NuMA and mInsc with LGN are mutually exclusive, with mInsc binding preferentially. Our results suggest that the Par3/mInsc/LGN and NuMA/LGN/Gαi complexes play sequential and partially overlapping roles in asymmetric cell division.

The mitotic apparatus protein NuMA has an intrinsic membrane-targeting mechanism that is regulated by CDK1-mediated phosphorylation, underlies anaphase-specific cortical accumulation of dynein, and contributes to chromosome separation.

Laparoscopic appendectomy is a useful tool in the treatment of acute appendicitis. Its advantages lie in its minimal invasiveness, its better cosmetic outcome, its lower rate of complications based on surgical expertise and state-of-the-art equipment. It can be recommended as an adoptable method for the routine patient with appendicitis.

The interaction between astral microtubules and the cell cortex is accompanied by constant cortical release and transport of LGN/dynein complex, which is modulated by cortical actin filaments. Regulated cortical release and transport of LGN/dynein complex along astral microtubules may contribute to spindle positioning in mammalian cells.