Congrats to lead author and Hehnly Lab graduate student Abrar (Abbi) Aljiboury on the acceptance of her study titled “Pericentriolar matrix (PCM) integrity relies on cenexin and Polo-Like Kinase (PLK)1” at Molecular Biology of the Cell. This work was a collaborative study between Hehnly Lab post baccalaureates Amra Mujcic and Erin Curtis, undergraduates Denise Magny and Thomas Cammerino, graduate student Yiling Lan, the Blatt imaging center manager Mike Bates, Hehnly Lab manager Judy Freshour, and Biology faculty member Yasir Ahmed-Braimeh. This study examined PLK1 activity and its association with maintaining the functional and physical properties of the centrosome's pericentriolar matrix (PCM). Here, Abbi and colleagues use a multimodal approach of human cells (HeLa), zebrafish embryos, and phylogenic analysis to test the role of a PLK1 binding protein, cenexin, in regulating the PCM. Their studies identify that cenexin is required for tempering microtubule nucleation by maintaining PCM cohesion in a PLK1 dependent manner. PCM architecture in cenexin-depleted zebrafish embryos was rescued with wild-type human cenexin, but not with a C-terminal cenexin mutant (S796A) deficient in PLK1 binding. They propose a model where cenexin's C-terminus acts in a conserved manner in eukaryotes, excluding nematodes and arthropods, to sequester PLK1 that limits PCM substrate phosphorylation events required for PCM cohesion.
Cenexin is needed for PCM cohesion. (A) Metaphase HeLa cells mitotic centrosomes labeled for centrosome markers: centrin, cenexin, Cep192, Pericentrin, Cep215 and γ-tubulin (Fire LUT) and MT marker, α-tubulin (grey). Control shRNA (top) and cenexin shRNA (bottom) treated cells shown. Scale bar, 5 μm. (B-F) Representative scatter plots depicting two-dimensional areas (μm2) of centrin (B), Cep192 (C), Pericentrin (D), Cep215 (E) and γ-tubulin (F) in control and cenexin shRNA treated metaphase cells. Mean with 95% confidence intervals shown. Unpaired, two-tailed Student’s t-tests, n.s. not significant, ***p<0.001, ****p<0.0001. (G) Control shRNA (top) and cenexin shRNA (bottom) metaphase cell projection. Centrin (grey), Cep215 (magenta) and DNA (DAPI, cyan) shown. Insets magnified 3x from G’ and G”. Scale bar, 5 μm. (H) Model depicting representative centrosome protein outline from a single representative mitotic centrosome reflecting changes resulting from cenexin-loss. Mean 2-dimensional areas (μm2) ±SD are provided.