Doublecortin Microtubule Affinity Is Regulated by a Balance of Kinase and Phosphatase Activity at the Leading Edge of Migrating Neurons

AbstractDoublecortin (Dcx) is a microtubule-associated protein that is mutated in X-linked lissencephaly (X-LIS), a neuronal migration disorder associated with epilepsy and mental retardation. Although Dcx can bind ubiquitously to microtubules in nonneuronal cells, Dcx is highly enriched in the leading processes of migrating neurons and the growth cone region of differentiating neurons. We present evidence that Dcx/microtubule interactions are negatively controlled by Protein Kinase A (PKA) and the MARK/PAR-1 family of protein kinases. In addition to a consensus MARK site, we identified a serine within a novel sequence that is crucial for the PKA- and MARK-dependent regulation of Dcx's microtubule binding activity in vitro. This serine is mutated in two families affected by X-LIS. Immunostaining neurons with an antibody that recognizes phosphorylated substrates of MARK supports the conclusion that Dcx localization and function are regulated at the leading edge of migrating cells by a balance of kinase and phosphatase activity

Aurora A activates D-TACC–Msps complexes exclusively at centrosomes to stabilize centrosomal microtubules

Centrosomes are the dominant sites of microtubule (MT) assembly during mitosis in animal cells, but it is unclear how this is achieved. Transforming acidic coiled coil (TACC) proteins stabilize MTs during mitosis by recruiting Minispindles (Msps)/XMAP215 proteins to centrosomes. TACC proteins can be phosphorylated in vitro by Aurora A kinases, but the significance of this remains unclear. We show that Drosophila melanogaster TACC (D-TACC) is phosphorylated on Ser863 exclusively at centrosomes during mitosis in an Aurora A–dependent manner. In embryos expressing only a mutant form of D-TACC that cannot be phosphorylated on Ser863 (GFP-S863L), spindle MTs are partially destabilized, whereas astral MTs are dramatically destabilized. GFP-S863L is concentrated at centrosomes and recruits Msps there but cannot associate with the minus ends of MTs. We propose that the centrosomal phosphorylation of D-TACC on Ser863 allows D-TACC–Msps complexes to stabilize the minus ends of centrosome-associated MTs. This may explain why centrosomes are such dominant sites of MT assembly during mitosis

Duodenoportal fistula caused by peptic ulcer after extended right hepatectomy for hilar cholangiocarcinoma

BACKGROUND: A fistula between the duodenum and the main portal vein near a peptic ulcer is extremely rare, and only two cases of duodenal ulcers have been reported in the past. CASE PRESENTATION: We report a 68-year-old man with a diagnosis of anemia who had a history of extended right hepatectomy for hilar cholangiocarcinoma 20 months previously. The first endoscopic examination revealed a giant peptic ulcer with active bleeding at the posterior wall of the duodenal bulbs, and hemostasis was performed. Endoscopic treatment and transarterial embolization were performed repeatedly because of uncontrollable bleeding from the duodenal ulcer. Nevertheless, he died of sudden massive hematemesis on the 20(th )hospital day. At autopsy, communication with the main portal vein and duodenal ulcer was observed. CONCLUSION: It should be borne in mind that the main portal vein is exposed at the front of the hepatoduodenal ligament in cases with previous extrahepatic bile duct resection

XMAP215 is a Processive Microtubule Polymerase

Fast growth of microtubules is essential for rapid assembly of the microtubule cytoskeleton during cell proliferation and differentiation. XMAP215 belongs to a conserved family of proteins that promote microtubule growth. To determine how XMAP215 accelerates growth, we developed a single-molecule assay to visualize directly XMAP215-GFP interacting with dynamic microtubules. XMAP215 binds free tubulin in a 1:1 complex that interacts with the microtubule lattice and targets the ends by a diffusion-facilitated mechanism. XMAP215 persists at the plus end for many rounds of tubulin subunit addition in a form of “tip-tracking.” These results show that XMAP215 is a processive polymerase that directly catalyzes the addition of up to 25 tubulin dimers to the growing plus end. Under some circumstances XMAP215 can also catalyze the reverse reaction, namely microtubule shrinkage. The similarities between XMAP215 and formins, actin polymerases, suggest that processive tip-tracking is a common mechanism for stimulating the growth of cytoskeletal polymers.Molecular and Cellular Biolog

Human cord blood-MNC transplantation improves PH

Objectives : To investigate the effects of human umbilical cord blood-derived mononuclear cell (hUCB-MNC) transplantation on pulmonary hypertension (PH) induced by monocrotaline (MCT) in immunodeficient mice and their distribution. Methods :MCT was administered to BALB/c Slc-nu/nu mice, and PH was induced in mice 4 weeks later. Fresh hUCB-MNCs harvested from a human donor after her delivery were injected intravenously into those PH mice. The medial thickness of pulmonary arterioles, ratio of right ventricular to septum plus left ventricular weight (RV/S+LV), and ratio of acceleration time to ejection time of pulmonary blood flow waveform (AT/ET) were determined 4 weeks after hUCB-MNC transplantation. To reveal the incorporation into the lung, CMTMR-labeled hUCB-MNCs were observed in the lung by fluorescent microscopy. DiR-labeled hUCB-MNCs were detected in the lung and other organs by bioluminescence images. Results : Medial thickness, RV/S+ LV and AT/ET were significantly improved 4 weeks after hUCB-MNC transplantation compared with those in mice without hUCB-MNC transplantation. CMTMR-positive hUCB-MNCs were observed in the lung 3 hours after transplantation. Bioluminescence signals were detected more strongly in the lung than in other organs for 24 hours after transplantation. Conclusions : The results indicate that hUCB-MNCs are incorporated into the lung early after hUCB-MNC transplantation and improve MCT-induced PH

Aurora A phosphorylation of TACC3/maskin is required for centrosome-dependent microtubule assembly in mitosis

Centrosomes act as sites of microtubule growth, but little is known about how the number and stability of microtubules emanating from a centrosome are controlled during the cell cycle. We studied the role of the TACC3–XMAP215 complex in this process by using purified proteins and Xenopus laevis egg extracts. We show that TACC3 forms a one-to-one complex with and enhances the microtubule-stabilizing activity of XMAP215 in vitro. TACC3 enhances the number of microtubules emanating from mitotic centrosomes, and its targeting to centrosomes is regulated by Aurora A–dependent phosphorylation. We propose that Aurora A regulation of TACC3 activity defines a centrosome-specific mechanism for regulation of microtubule polymerization in mitosis

Quantitative Features of serum sIL-2R level in Patients with Mature B-Cell Lymphoma? Involvement of LDH

Serum Lactate Dehydrogenase (LDH) activity and soluble IL-2 Receptor-alpha (sIL-2R) levels are monitored as a marker ofdisease activity in patients with lymphoma. Although adult T-cell leukemia (ATL) cells are well known to release large amounts ofsIL-2R,it remains unclear to what extent B-cell lymphoma cells shed sIL-2R in sera. Subtypes of mature B-cell lymphoma, includingCD25+ hairy leukemic cells, were examined for the characteristics of sIL-2R levels in each subtype. In normal controls, theserum sIL-2R mean value was 260u/mL.The median serum sIL-2R value for 64 B-cell lymphoma cases was 506 u/mL;by subtypethe median values were as follows: 1157 u/mL for 7 cases of chronic lymphocytic leukemia/hairy cell leukemia (CLL/HCL), 451u/mL for 38 cases of diffuse large B-cell lymphoma (DLBCL), and 456 u/mL for 19 cases of follicular Lymphoma (FL). The medianvalues of serum LDH activity by the above subtypes were 175 IU/mL, 204 IU/mL, and 198 IU/mL, respectively. There wasdistinct inter-subtype and inter-patient variation of serum sIL-2R.In particular, inter-case variation could be grouped into value forthree concentration ranges: less than 300 u/mL, 300-1000 u/mL, and greater than 1000 u/mL. Cases with serum sIL-2R valuesof 1000 u/mL or more tended to have an especially high sIL-2R to LDH ratio, suggesting a close relationship between high sIL-2Rand CD25-expressing lymphoma cells. With respect to sIL-2R and LDH levels, CLL/HCL, DLBCL, and FL showed similar distributions.Moreover, for sIL-2R levels exceeding 1000u/mL, sIL-2R levels were randomly high according to the LDH status. Conclusively,the combination of serum sIL-2R level and LDH activity can provide a better understanding of characteristics of subtypesof mature B-Cell Lymphoma and can be used as a reliable surrogate marker for evaluating numerical and biological data

Baastrup's Disease Is Associated with Recurrent of Sciatica after Posterior Lumbar Spinal Decompressions Utilizing Floating Spinous Process Procedures

Study DesignRetrospective case-control study.PurposeTo determine whether kissing spine is a risk factor for recurrence of sciatica after lumbar posterior decompression using a spinous process floating approach.Overview of LiteratureKissing spine is defined by apposition and sclerotic change of the facing spinous processes as shown in X-ray images, and is often accompanied by marked disc degeneration and decrement of disc height. If kissing spine significantly contributes to weight bearing and the stability of the lumbar spine, trauma to the spinous process might induce a breakdown of lumbar spine stability after posterior decompression surgery in cases of kissing spine.MethodsThe present study included 161 patients who had undergone posterior decompression surgery for lumbar canal stenosis using a spinous process floating approaches. We defined recurrence of sciatica as that resolved after initial surgery and then recurred. Kissing spine was defined as sclerotic change and the apposition of the spinous process in a plain radiogram. Preoperative foraminal stenosis was determined by the decrease of perineural fat intensity detected by parasagittal T1-weighted magnetic resonance imaging. Preoperative percentage slip, segmental range of motion, and segmental scoliosis were analyzed in preoperative radiographs. Univariate analysis followed by stepwise logistic regression analysis determined factors independently associated with recurrence of sciatica.ResultsStepwise logistic regression revealed kissing spine (p=0.024; odds ratio, 3.80) and foraminal stenosis (p<0.01; odds ratio, 17.89) as independent risk factors for the recurrence of sciatica after posterior lumbar spinal decompression with spinous process floating procedures for lumbar spinal canal stenosis.ConclusionsWhen a patient shows kissing spine and concomitant subclinical foraminal stenosis at the affected level, we should sufficiently discuss the selection of an appropriate surgical procedure

Baastrup\u27s Disease Is Associated with Recurrent of Sciatica after Posterior Lumbar Spinal Decompressions Utilizing Floating Spinous Process Procedures

Study DesignRetrospective case-control study.PurposeTo determine whether kissing spine is a risk factor for recurrence of sciatica after lumbar posterior decompression using a spinous process floating approach.Overview of LiteratureKissing spine is defined by apposition and sclerotic change of the facing spinous processes as shown in X-ray images, and is often accompanied by marked disc degeneration and decrement of disc height. If kissing spine significantly contributes to weight bearing and the stability of the lumbar spine, trauma to the spinous process might induce a breakdown of lumbar spine stability after posterior decompression surgery in cases of kissing spine.MethodsThe present study included 161 patients who had undergone posterior decompression surgery for lumbar canal stenosis using a spinous process floating approaches. We defined recurrence of sciatica as that resolved after initial surgery and then recurred. Kissing spine was defined as sclerotic change and the apposition of the spinous process in a plain radiogram. Preoperative foraminal stenosis was determined by the decrease of perineural fat intensity detected by parasagittal T1-weighted magnetic resonance imaging. Preoperative percentage slip, segmental range of motion, and segmental scoliosis were analyzed in preoperative radiographs. Univariate analysis followed by stepwise logistic regression analysis determined factors independently associated with recurrence of sciatica.ResultsStepwise logistic regression revealed kissing spine (p=0.024; odds ratio, 3.80) and foraminal stenosis (p<0.01; odds ratio, 17.89) as independent risk factors for the recurrence of sciatica after posterior lumbar spinal decompression with spinous process floating procedures for lumbar spinal canal stenosis.ConclusionsWhen a patient shows kissing spine and concomitant subclinical foraminal stenosis at the affected level, we should sufficiently discuss the selection of an appropriate surgical procedure