Distinct Mitotic Functions of Nucleolar and Spindle-Associated Protein 1 (NuSAP1) Are Controlled by Two Consensus SUMOylation Sites

Nucleolar and Spindle-Associated Protein 1 (NuSAP1) is an important mitotic regulator, implicated in control of mitotic microtubule stability and chromosome segregation. NuSAP1 regulates these processes by interacting with several protein partners. Its abundance, activity and interactions are therefore tightly regulated during mitosis. Protein conjugation with SUMO (Small Ubiquitin-like MOdifier peptide) is a reversible post-translational modification that modulates rapid changes in the structure, interaction(s) and localization of proteins. NuSAP1 was previously found to interact with RANBP2, a nucleoporin with SUMO ligase and SUMO-stabilizing activity, but how this interaction affects NuSAP1 activity has remained elusive. Here, we show that NuSAP1 interacts with RANBP2 and forms proximity ligation products with SUMO2/3 peptides in a RANBP2-dependent manner at key mitotic sites. A bioinformatic search identified two putative SUMO consensus sites in NuSAP1, within the DNA-binding and the microtubule-binding domains, respectively. Site-specific mutagenesis, and mitotic phenotyping in cell lines expressing each NuSAP1 mutant version, revealed selective roles of each individual site in control of NuSAP1 localization and in generation of specific mitotic defects and distinct fates in daughter cells. These results identify therefore two new regulatory sites for NuSAP1 functions and implicate RANBP2 in control of NuSAP1 activity.

RS6077 induces mitotic arrest and selectively activates cell death in human cancer cell lines and in a lymphoma tumor in vivo

We synthesized a new inhibitor of tubulin polymerization, the pyrrole (1-(7H-pyrrolo[2,3- d]pyrimidin-4-yl)-1H-pyrrol-3-yl)(3,4,5-trimethoxy-phenyl)methanone 6 (RS6077). Compound 6 inhibited the growth of multiple cancer cell lines, with IC₅₀ values in the nM range, without affecting the growth of non-transformed cells. The novel agent arrested cells in the G2/M phase of the cell cycle in both transformed and non-transformed cell lines, but single cell analysis by time-lapse video recording revealed a remarkable selectivity in cell death induction by compound 6: in RPE-1 non-transformed cells mitotic arrest induced was not necessarily followed by cell death; in contrast, in HeLa transformed and in lymphoid-derived transformed AHH1 cell lines, cell death was effectively induced during mitotic arrest in cells that fail to complete mitosis. Importantly, the agent also inhibited the growth of the lymphoma TMD8 xenograft model. Together these findings suggest that derivative 6 has a selective efficacy in transformed vs non-transformed cells and indicate that the same compound has potential as novel therapeutic agent to treat lymphomas. Compound 6 showed good metabolic stability upon incubation with human liver microsomes.

Non-transport roles of nuclear import receptors: In need of the right balance

Nuclear import receptors ensure the recognition and transport of proteins across the nuclear envelope into the nucleus. In addition, as diverse processes as mitosis, post-translational modifications at mitotic exit, ciliogenesis, and phase separation, all share a common need for regulation by nuclear import receptors - particularly importin beta-1 and importin beta-2/transportin - independent on nuclear import. In particular, 1) nuclear import receptors regulate the mitotic spindle after nuclear envelope breakdown, 2) they shield cargoes from unscheduled ubiquitination, regulating their timely proteolysis; 3) they regulate ciliary factors, crucial to cell communications and tissue architecture during development; and 4) they prevent phase separation of toxic proteins aggregates in neurons. The balance of nuclear import receptors to cargoes is critical in all these processes, albeit in opposite directions: overexpression of import receptors, as often found in cancer, inhibits cargoes and impairs downstream processes, motivating the therapeutic design of specific inhibitors. On the contrary, elevated expression is beneficial in neuronal contexts, where nuclear import receptors are regarded as potential therapeutic tools in counteracting the formation of aggregates that may cause neurodegeneration. This paradox demonstrates the amplitude of nuclear import receptors-dependent functions in different contexts and adds complexity in considering their therapeutic implications.

Migraine and obesity: metabolic parameters and response to a weight loss programme

BACKGROUND AND OBJECTIVE

Weight loss can determine significant improvement of migraine in obese patients. Herein, we evaluated a clinical sample of adolescent migraineurs with obesity who participated in an interdisciplinary programme for weight loss, in order to identify possible metabolic parameters associated with good migraine control.

SUBJECTS AND METHODS

Using a cross-sectional design, we evaluated 112 out of 135 adolescents who previously underwent our intervention programme. Based on persistence of headache, subjects for comparison were 40 migraine-free and 72 not migraine-free adolescents. Participants underwent anthropometric evaluations and biochemical tests.

RESULTS

Patients with persistence of migraine had significantly higher weight (P < 0.01), body mass index (P < 0.01), waist circumference (P < 0.01), homeostasis model assessment of insulin resistance (P < 0.001), triglyceride (P < 0.05), total cholesterol (P < 0.05) and low-density lipoprotein cholesterol (P < 0.05) values when compared with those who became migraine-free. Between potential predictors, only insulin resistance (odds ratio = 3.5, 95% confidence interval = 1.4-6.1; P <  0.001) was significantly associated with persistence of migraine after intervention programme.

CONCLUSIONS

Among obese adolescents with migraine who underwent an intervention programme for weight loss, patients who did not become migraine-free showed higher adiposity values than those who became migraine-free. Patients with insulin resistance had 3.5 times the odds of having persistence of migraine compared with those without.

The Golgi apparatus of spinal ganglion neurons: quantitative changes with aging

The Golgi apparatus of spinal ganglion neurons was studied in 1, 3.6, 6.7, and 8.8-year-old rabbits. The structure of this organelle did not differ in the four age groups examined. While the mean volume of the neuronal perikaryon increased progressively with age, the total volume of the Golgi apparatus remained stable throughout life. As a consequence, the mean percentage of perikaryal volume occupied by this organelle decreased significantly with age. Since the percentage of perikaryal volume occupied by lipofuscin remained at low levels throughout life, the ratio of the total volume of the Golgi apparatus to the functionally active volume of cytoplasm decreased with age. It is possible that this decrease is related to the reduction in neuronal metabolism that occurs in senescence. The age-related quantitative changes in the Golgi apparatus were very similar in large light and in small dark neurons. Finally, neither fragmentation, nor peripheral displacement of the Golgi apparatus was observed with advancing age.

The Golgi apparatus of satellite cells associated with spinal ganglion neurons: changes with age in the rabbit

We studied the Golgi apparatus in the satellite cell sheaths enveloping spinal ganglion neurons of rabbits aged 12, 42, and 79 months. We found neither structural changes nor indications of peripheral displacement of this organelle with advancing age. The mean percentage of cytoplasmic volume occupied by the Golgi apparatus decreased significantly passing from young adult to old rabbits. This decrease was only in very minor part a consequence of lipofuscin accumulation, so that the ratio between the total volume of the Golgi apparatus and the functionally active volume of cytoplasm decreased with age. The mean cytoplasmic volume of perineuronal satellite cell sheaths did not change significantly with increasing age, whereas the total volume of the Golgi apparatus within these sheaths decreased significantly with age. This decrease strongly suggests that the activity of satellite cells diminishes in old age, further suggesting that these cells are unable to compensate for the decrease in the neuronal metabolism that a number of authors have described in old age.

Changes with age in the Golgi apparatus of rabbit spinal ganglion neurons

We studied the Golgi apparatus in spinal ganglion neurons of rabbits aged 12, 42 and 79 months. We found no structural changes, no indications of fragmentation, no indications of peripheral displacement affecting this organelle with advancing age. The volume of the perikaryon increased significantly with age, whereas the total volume of the Golgi apparatus remained essentially constant. Hence the mean percentage of perikaryal volume occupied by the Golgi apparatus decreased with age. This decrease was only in very minor part a consequence of lipofuscin accumulation, so that the ratio between the total volume of the Golgi apparatus and the functionally active volume of cytoplasm decreased with age. This decrease could be related to the reduced neuronal metabolism that occurs during ageing. It is possible that the delivery to the axon of newly synthesized proteins destined for fast transport is one of the Golgi apparatus roles that decrease with age. Finally, we found that the age-related quantitative changes in the Golgi apparatus did not differ between large light and small dark neurons.

Decrease in the nucleo-cytoplasmic volume ratio of rabbit spinal ganglion neurons with age

Nuclear and perikaryal volumes, as well as the mean percentage of perikaryal volume occupied by lipofuscin, were estimated in spinal ganglion neurons of 12, 42 and 79 month-old rabbits. The volume ratio between nucleus and perikaryal cytoplasm (N/C volume ratio) decreased progressively and significantly with increasing age. This was not a consequence of the perikaryal enlargement due to the age-related lipofuscin accumulation since the same result was obtained when the volume occupied by lipofuscin was subtracted from the perikaryal volume. The decrease in the N/C volume ratio may depend on an age-related loss of DNA, a cytoplasmic influence on nuclear size, or other unknown causes.

Amount and distribution of lipofuscin in nerve and satellite cells from spinal ganglia of young adult and aged rabbits

The quantitative aspects of the age-related accumulation of lipofuscin were studied in the rabbit spinal ganglia by stereological methods using the electron microscope. Both neurons and their associated satellite cells were examined. In neurons, the shape and structure of lipofuscin bodies differed in young adults (12-months-old) compared to aged rabbits (79-months-old), whereas substantial changes were not observed in satellite cells. Both in nerve and satellite cells, lipofuscin bodies were scattered singly in young adults, but were often clustered in old animals. Lipofuscin occupied an average of 0.36% of neuronal perikaryal volume in the young adults and 2.55% in the aged rabbits; these percentages are much lower than those observed in the same neurons of other species. In the satellite cells, the corresponding values were 0.29% and 2.02%. In the young adults, the mean size of lipofuscin bodies was significantly greater in neurons than in satellite cells; the size of these bodies increased with age by about 2.7 times in neurons and by about 1.7 times in satellite cells. Consequently, in the old rabbits the mean size of lipofuscin bodies was about 2.2 times greater in neurons than in satellite cells. It has been suggested that lipofuscin bodies are transferred from the neuronal perikaryon to the surrounding satellite cells and then removed via the capillaries. However, the present findings suggest that lipofuscin located in satellite cells represents pigment formed by these cells rather than being transferred from neuronal perikaryon. It would appear that the age-related accumulation of lipofuscin in the rabbit spinal ganglia has little effect on neuronal metabolism.

Clomipramine in the elderly: tolerance and plasma levels

Five elderly, treatment-resistant, depressed, female patients were closely monitored in a research setting during treatment with clomipramine. Plasma clomipramine levels were determined to establish a steady state. Elderly patients (67 to 80 years old) reached a therapeutic steady state at doses lower than that reported for midlife patients. Overall, clomipramine was well tolerated in this group. Depression, measured by the Hamilton Rating Scale for Depression, decreased 42%, and the frequency of somatic complaints, measured by the Rating Scale for Side Effects, declined by 57%. Clomipramine is specifically indicated for the treatment of obsessive-compulsive disorder and may be an alternative for elderly depressed patients, provided that lower doses and plasma clomipramine monitoring are used.