Hierarchical recruitment of Plk4 and regulation of centriole biogenesis by two centrosomal scaffolds,Cep192 and Cep152

Centrosomes play an important role in various cellular processes, including spindle formation and chromosome segregation. They are composed of two orthogonally arranged centrioles, whose duplication occurs only once per cell cycle. Accurate control of centriole numbers is essential for the maintenance of genomic integrity. Although it is well appreciated that polo-like kinase 4 (Plk4) plays a central role in centriole biogenesis, how it is recruited to centrosomes and whether this step is necessary for centriole biogenesis remain largely elusive. Here we showed that Plk4 localizes to distinct subcentrosomal regions in a temporally and spatially regulated manner, and that Cep192 and Cep152 serve as two distinct scaffolds that recruit Plk4 to centrosomes in a hierarchical order. Interestingly, Cep192 and Cep152 competitively interacted with the cryptic polo box of Plk4 through their homologous N-terminal sequences containing acidic-α-helix and N/Q-rich motifs. Consistent with these observations, the expression of either one of these N-terminal fragments was sufficient to delocalize Plk4 from centrosomes. Furthermore, loss of the Cep192- or Cep152-dependent interaction with Plk4 resulted in impaired centriole duplication that led to delayed cell proliferation. Thus, the spatiotemporal regulation of Plk4 localization by two hierarchical scaffolds, Cep192 and Cep152, is critical for centriole biogenesis.The centrosome is the main microtubule-organizing center in mammalian cells that plays a central role in spindle formation and chromosome segregation during mitosis. Centrosomes are composed of two orthogonally arranged centrioles surrounded by an amorphous mass of electron-dense pericentriolar material (PCM). Centrioles duplicate precisely once per cell cycle and serve as platforms for the assembly of centrosomes, primary cilia, and flagella (1–4).Centriole duplication is initiated by the assembly of a procentriole in early S phase. In Caenorhabditis elegans, a centrosomal scaffold protein, called Spd-2, is required for proper recruitment of a Ser/Thr kinase, Zyg-1 (5), to centrosomes, and this step in turn allows the recruitment of Sas-6, Sas-5, and Sas-4 to the site of procentriole assembly (6, 7). Sas6 plays a pivotal role in self-assembling a cartwheel-like structure at this site of the procentriole with Sas5 and Sas4 (8–12). In Drosophila, the overexpression of polo-like kinase 4 (Plk4; also called Sak), the Zyg-1 ortholog, is sufficient to induce centriole amplification, whereas the depletion of Plk4 disrupts centriole duplication (12, 13). Interestingly, however, Drosophila Spd-2 is dispensable for Plk4-mediated centriole duplication (14). Instead, another scaffold, Asterless, has been suggested to play a critical role in targeting Plk4 to centrosomes (15), hinting that the mechanism underlying Plk4 recruitment is distinct in different organisms.Accumulated evidence in humans suggests that Plk4 is a functional ortholog of C. elegans Zyg-1 and Drosophila Plk4, and that it plays a key role in centriole duplication (16, 17). When overexpressed, Plk4 can induce multiple centriole precursors surrounding a single parental centriole, and centrosomally localized Plk4 appears to be required for this event (16). The cryptic polo box (CPB) present at the upstream of the C-terminal polo box (PB) (18) is necessary and sufficient for targeting Plk4 to centrosomes (16, 19). Interestingly, the CPB comprises two structurally related motifs and forms a homodimer (19) to interact with its binding targets. However, the molecular basis of how Plk4 binds to its targets and localizes to centrosomes remains largely elusive.Studies have shown that Cep152, a human ortholog of Drosophila Asterless, interacts with Plk4 through the CPB (20, 21). However, the depletion of Cep152 does not significantly decrease the level of Plk4 at centrosomes. Recently, Sonnen et al. have shown that a C. elegans Spd-2 ortholog, Cep192, interacts with Plk4 and promotes the recruitment of Plk4 to centrosomes (22). Moreover, Cep192 binds to Cep152, and the depletion of both enhances the Plk4 localization defect (22). Based on these observations, Sonnen et al. proposed that Cep192 cooperates with Cep152 to properly recruit Plk4 to centrosomes and to promote centriole duplication (22).In this study, we demonstrated that disrupting either the Cep192–Plk4 interaction or the Cep152–Plk4 interaction was sufficient to impair centriole duplication. We further showed that Plk4 dynamically localizes to different subcentrosomal regions in a cell cycle-specific manner, and that Cep192 functions at a point upstream of Cep152 to regulate Plk4 localization. Thus, we propose that the spatiotemporal regulation of Plk4 localization by two hierarchical scaffolds, Cep192 and Cep152, is critical for Plk4-dependent centriole biogenesis.     

Mosquito larvicidal and pupicidal activity of Euphorbia hirta Linn. (Family: Euphorbiaceae) and Bacillus sphaericus against Anopheles stephensi Liston. (Diptera: Culicidae)

ObjectiveTo explore the larvicidal and pupicidal activity of Euphorbia hirta (E. hirta) leaf extract and Bacillus sphaericus (B. sphaericus) against the malarial vector, Anopheles stephensi (An. stephensi).MethodsThe larvicidal and pupicidal activity was assayed against An. stephensi at various concentrations ranging from (75-375 ppm) under the laboratory as well as field conditions. The LC₅₀ and LC₉₀ value of the E. hirta leaf extract was determined by probit analysis.ResultsThe plant extract showed larvicidal effects after 24 h of exposure; however, the highest larval mortality was found in the methanol extract of E. hirta against the first to fourth instars larvae and pupae of values LC₅₀= 137.40, 172.65, 217.81, 269.37 and 332.39 ppm; B. sphaericus against the first to fourth instars larvae and pupae of values LC₅₀= 44.29, 55.83, 68.51, 82.19 and 95.55 ppm, respectively. Moreover, combined treatment of values of LC₅₀= 79.13, 80.42, 86.01, 93.00 and 98.12 ppm, respectively. No mortality was observed in the control.ConclusionsThese results suggest methanol leaf extracts of E. hirta and B. sphaericus have potential to be used as an ideal eco-friendly approach for the control of the malarial vector, An. stephensi as target species of vector control programs. This study provides the first report on the combined mosquito larvicidal and pupicidal activity of this plant crude extract and bacterial toxin against An. stephensi mosquitoes.     

Toxicity effect of Delonix elata (Yellow Gulmohr) and predatory efficiency of Copepod,Mesocyclops aspericornis for the control of dengue vector,Aedes aegypti

Objective

To evaluate the toxicity, predatory efficiency of Delonix elata (D. elata) and Mesocyclops aspericornis (M. aspericornis) against dengue vector, Aedes aegypti (Ae. aegypti).

Methods

A mosquitocidal bioassay was conducted at different concentration of plant extract followed by WHO standard method. The probit analysis of each tested concentration and control were observed by using software SPSS 11 version package. The each tested concentration variable was assessed by DMRT method. The predatory efficiency of copepod was followed by Deo et al., 1988. The predator, M. aspericornis was observed for mortality, abnormalities, survival and swimming activity after 24 h treatment of plant and also predation on the mosquito larvae were observed.

Results

D. elata were tested for biological activity against the larvae, and pupae of Ae. aegypti. Significant mortality effects were observed in each life stage. The percentage of mortality was 100% in first and second instars whereas 96%, 92% in third and fourth instars. Fitted probit-mortality curves for larvae indicated the median and 90% lethal concentrations of D. elata for instars 1-4 to be 4.91 (8.13), 5.16 (8.44), 5.95 (7.76) and 6.87 (11.23), respectively. The results indicate that leaf extract exhibits significant biological activity against life stages. The present study revealed that D. elata is potentially important in the control of Ae. aegypti. Similar studies were conducted for predatory efficiency of Copepod, M. aspericornis against mosquito vector Ae. Aegypti. This study reported that the predatory copepod fed on 39% and 25% in I and III instar larvae of mosquito and in combined treatment of D. elata and copepod maximum control of mosquito larval states and at 83%, 80%, 75% and 53% in I, II, III and IV instars, respectively.

Conclusions

The combined action of plant extract and predatory copepod to effectively control mosquito population and reduce the dengue transmitting diseases.     

Studies on defluoridation of water by tamarind seed, an unconventional biosorbent

Tamarind seed, a household waste from the kitchen is used for the sorptive removal of fluoride from synthetic aqueous solution as well as from field water samples. Batch sorptive defluoridation was conducted under variable experimental conditions such as pH, agitation time, initial fluoride concentration, particle size and sorbent dose. Maximum defluoridation was achieved at pH 7.0. Defluoridation capacity decreases with increase in temperature and particle size. Further, defluoridation follows first order kinetics and Langmuir adsorption isotherm. Desorption was carried out with 0.1 N HCl and is 90 per cent. The surface and sorption characteristics were analysed using FTIR and SEM techniques. All these results indicate the involvement of energetic forces such as coulombic interaction in sorption. For domestic and industrial applications, defluoridation with 100% achievement and subsequent regeneration of adsorbent was performed with a household water filter and fixed bed column respectively.     

Tetrahydrocurcumin: effect on chloroquine-mediated oxidative damage in rat kidney

Tetrahydrocurcumin is an antioxidative substance, which is derived from curcumin, the component of turmeric. In the present investigation, the effect of tetrahydrocurcumin and curcumin against chloroquine-induced nephrotoxicity were studied in female wistar rats. Oral administration of tetrahydrocurcumin significantly prevented the occurrence of chloroquine (970 mg/kg body weight)-induced renal damage. Upon administration of tetrahydrocurcumin to chloroquine-treated rats, the level of lipid peroxidation was significantly decreased while the levels of non-enzymic and enzymic antioxidants were significantly increased in kidney. Oral administration (80 mg/kg body weight) attenuated the chloroquine-induced nephrotoxicity by significantly decreased levels of serum urea and creatinine with significant normalization of creatinine clearance. On administration of tetrahydrocurcumin, the depleted renal antioxidant defense system (enzymatic and non-enzymatic antioxidants) was significantly increased in rats treated with chloroquine. These biochemical observations were supplemented by histopathological examination of kidney section. These results suggest that administration of chloroquine imposes an oxidative stress to renal tissue and that tetrahydrocurcumin protects the oxidative damage associated with chloroquine.     

Effect of tetrahydrocurcumin on lipid peroxidation and lipids in streptozotocin-nicotinamide-induced diabetic rats

Hyperlipidaemia is an associated complication of diabetes mellitus. We recently reported that tetrahydrocurcumin lowered the blood glucose in diabetic rats. In the present study, we have investigated the effect of tetrahydrocurcumin, one of the active metabolites of curcumin on lipid profile and lipid peroxidation in streptozotocin-nicotinamide-induced diabetic rats. Tetrahydrocurcumin 80 mg/kg body weight was administered orally to diabetic rats for 45 days, resulted a significant reduction in blood glucose and significant increase in plasma insulin in diabetic rats, which proved its antidiabetic effect. Tetrahydrocurcumin also caused a significant reduction in lipid peroxidation (thiobarbituric acid reactive substances and hydroperoxides) and lipids (cholesterol, triglycerides, free fatty acids and phospholipids) in serum and tissues, suggesting its role in protection against lipid peroxidation and its antihyperlipidemic effect. Tetrahydrocurcumin showed a better effect when compared with curcumin. Results of the present study indicate that tetrahydrocurcumin showed antihyperlipidaemic effect in addition to its antidiabetic effect in type 2 diabetic rats.     

Heart surgery in infants with hemophilia

We describe 2 infants with hemophilia A who had heart surgery under cardiopulmonary bypass with factor VIII replacement therapy, and we recommend a guideline for factor VIII support for cardiac surgery. One child had repair of total anomalous pulmonary venous connection. The second had cardiac catheterization followed by repair of ventricular septal defect and total anomalous pulmonary venous connection. Close collaboration between hematologist, laboratory, cardiologist, and cardiac surgeon is crucial in successful management of coagulation abnormalities during and after surgery.     

Plasma CRP level predicts left ventricular function and exercise capacity in patients with acute myocardial infarction

BACKGROUND: C-reactive protein estimation can help in predicting short- and long-term prognosis after acute myocardial infarction. High plasma C-reactive protein level in the acute phase strongly indicates a poor clinical outcome of the patients with myocardial infarction. METHODS AND RESULTS: One hundred consecutive patients admitted with ST elevation myocardial infarction in the intensive coronary care unit in our hospital who were able to do symptom-limited treadmill test during early recovery phase were studied. Plasma C-reactive protein was measured at the time of admission by immunoturbidity method. The normal value of the C-reactive protein was taken as 0.8 mg/dl. Echocardiographic study was done on day three of admission and ejection fraction was estimated by modified Simpson's method. Symptom-limited treadmill exercise test was done in all the patients. Patients were classified into two groups based on level of C-reactive protein: those with low C-reactive protein level (1.26 +/- 0.91 mg/dl, n=40) and those with high C-reactive protein level (6.52 +/- 3.97 mg/dl, n=60). Ejection fraction was lower in high C-reactive protein group (46.7 +/- 11.9%) compared to low C-reactive protein group (56.9 +/- 7.7%) (p = 0.011). Exercise capacity was lower in high C-reactive protein group (2.8 +/- 1.4 METs) compared to low C-reactive protein group (5.5 +/- 2.5 METs) p = 0.027). CONCLUSIONS: C-reactive protein levels are an index of the severity of myocardial necrosis which translate to worse left ventricular function. Higher the C-reactive protein level, lower the ejection fraction and worse may be the prognosis.     

In vivo tumor imaging using polo-box domain of polo-like kinase 1 targeted peptide

Polo-like kinase 1 (Plk1) is a regulator of cell cycle progression during mitosis; it is overexpressed in many different tumors and has been implicated as a potential antimitotic target. Plks are characterized by the presence of a highly conserved C-terminal polo-box domain (PBD) that is involved in regulating kinase activity. The phosphopeptide Pro-Leu-His-Ser-p-Thr (PLHSpT) is a potent selective inhibitor of the PBD of human plk1 that acts by inducing mitotic arrest and apoptotic cell death in cancer cells. We synthesized cRGDyK-S-S-CPLHSpT to exploit the drug delivery and molecular imaging using positron emission tomography (PET). The peptide was blocked dramatically proliferation of tumor in?vitro and in?vivo. It was attempted to develop and show a tumor PET image with the radiolabeled-peptide. Here we showed the peptide is promising not only as an anticancer drug, but also as a radioligand for tumor diagnosis with PET. We expect that our contribution will provide new insights into the design of Plk1 peptide inhibitors and have significant implications for anticancer therapy and tumor diagnosis.