A better understanding of the molecules implicated in the growth and survival of glioblastoma (GBM) cells and their response to temozolomide (TMZ), the standard-of-care chemotherapeutic agent, is necessary for the development of new therapies that would improve the outcome of current GBM treatments. In this study, we characterize the role of pericentriolar material 1 (PCM1), a component of centriolar satellites surrounding centrosomes, in GBM cell proliferation and sensitivity to genotoxic agents such as TMZ. We show that PCM1 is expressed around centrioles and ciliary basal bodies in patient GBM biopsies and derived cell lines and that its localization is dynamic throughout the cell cycle. To test whether PCM1 mediates GBM cell proliferation and/or response to TMZ, we used CRISPR/Cas9 genome editing to generate primary GBM cell lines depleted of PCM1. These PCM1-depleted cells displayed reduced AZI1 satellite protein localization and significantly decreased proliferation, which was attributable to increased apoptotic cell death. Furthermore, PCM1-depleted lines were more sensitive to TMZ toxicity than control lines. The increase in TMZ sensitivity may be partly due to the reduced ability of PCM1-depleted cells to form primary cilia, as depletion of KIF3A also ablated GBM cells' ciliogenesis and increased their sensitivity to TMZ while preserving PCM1 localization. In addition, the co-depletion of KIF3A and PCM1 did not have any additive effect on TMZ sensitivity. Together, our data suggest that PCM1 plays multiple roles in GBM pathogenesis and that associated pathways could be targeted to augment current or future anti-GBM therapies.

The primary cilia of forebrain neurons assemble around birth and become enriched with neuromodulatory receptors. Our understanding of the permanence of these structures and their associated signaling pathways in the aging brain is poor, but they are worthy of investigation because disruptions in neuronal cilia signaling have been implicated in changes in learning and memory, depression-like symptoms, and sleep anomalies. Here, we asked whether neurons in aged forebrain retain primary cilia and whether the staining characteristics of aged cilia for type 3 adenylyl cyclase (ACIII), somatostatin receptor 3 (SSTR3), and pericentrin resemble those of cilia in younger forebrain. To test this, we analyzed immunostained sections of forebrain tissues taken from young and aged male Fischer 344 (F344) and F344 × Brown Norway (F344 × BN) rats. Analyses of ACIII and SSTR3 in young and aged cortices of both strains of rats revealed that the staining patterns in the neocortex and hippocampus were comparable. Virtually every NeuN positive cell examined possessed an ACIII positive cilium. The lengths of ACIII positive cilia in neocortex were similar between young and aged for both strains, whereas in F344 × BN hippocampus, the cilia lengths increased with age in CA1 and CA3, but not in dentate gyrus (DG). Additionally, the percentages of ACIII positive cilia that were also SSTR3 positive did not differ between young and aged tissues in either strain. We also found that pericentrin, a protein that localizes to the basal bodies of neuronal cilia and functions in primary cilia assembly, persisted in aged cortical neurons of both rat strains. Collectively, our data show that neurons in aged rat forebrain possess primary cilia and that these cilia, like those present in younger brain, continue to localize ACIII, SSTR3, and pericentrin. Further studies will be required to determine if the function and signaling pathways regulated by cilia are similar in aged compared to young brain.

in white-eyed Drosophila maintained under artificial light. Here we tested whether protein levels at rhabdoms change significantly in the highly pigmented lateral eyes of wild-caught Limulus polyphemus maintained in natural diurnal illumination and whether these changes are under circadian control. We found that rhabdomeral levels of opsins (Ops1-2), the G protein activated by rhodopsin (G q α) and arrestin change significantly from day to night and that nighttime levels of each protein at rhabdoms are significantly influenced by signals from the animalʼs central circadian clock. Clock input at night increases Ops1-2 and G q α and decreases arrestin levels at rhabdoms. Clock input is also required for a rapid decrease in rhabdomeral Ops1-2 beginning at sunrise. We found further that dark adaptation during the day and the night are not equivalent. During daytime dark adaptation, when clock input is silent, the increase of Ops1-2 at rhabdoms is small and G q α levels do not increase. However, increases in Ops1-2 and G q α at rhabdoms are enhanced during daytime dark adaptation by treatments that elevate cAMP in photoreceptors, suggesting that the clock influences dark-adaptive increases in Ops1-2 and G q α at Limulus rhabdoms by activating cAMP-dependent processes. The circadian regulation of Ops1-2 and G q α levels at rhabdoms probably has a dual role: to increase retinal sensitivity at night and to protect photoreceptors from light damage during the day.