Kazutaka Sumita

Synaptic scaffolding molecule (S-SCAM) membrane-associated guanylate kinase with inverted organization (MAGI)-2 is associated with cell adhesion molecules at inhibitory synapses in rat hippocampal neurons

Synaptic scaffolding molecule (S‐SCAM) is a synaptic protein, which harbors five or six PSD‐95/Discs large/ZO‐1 (PDZ), a guanylate kinase and two WW domains. It interacts with NMDA receptor subunits, neuroligin and β‐catenin, and is involved in the accumulation of neuroligin at excitatory synapses. In this study, we have demonstrated S‐SCAM is localized at inhibitory synapses in rat primary cultured hippocampal neurons. We have identified β‐dystroglycan (β‐DG) as a binding partner for S‐SCAM at inhibitory synapses. WW domains of S‐SCAM bind to three sequences of β‐DG. We have also revealed that S‐SCAM can interact with neuroligin 2, which is known to be exclusively localized at inhibitory synapses. The WW domains and the second PDZ domain of S‐SCAM are involved in the interaction with neuroligin 2. β‐DG, neuroligin 2 and S‐SCAM form a tripartite complex in vitro. Neuroligin 2 is detected in the immunoprecipitates by anti‐β‐DG antibody from rat brain. S‐SCAM, β‐DG and neuroligin 2 are partially co‐localized in rat hippocampal neurons. These data suggest that S‐SCAM is associated with β‐DG and neuroligin 2 at inhibitory synapses, and functions as a linker between the dystrophin glycoprotein complex and the neurexin–neuroligin complex.

Threonine 74 of MOB1 is a putative key phosphorylation site by MST2 to form the scaffold to activate nuclear Dbf2-related kinase 1.

Mammalian nuclear Dbf2-related (NDR) kinases (LATS1 and 2, NDR1 and 2) play a role in cell proliferation, apoptosis and morphological changes. These kinases are regulated by mammalian sterile 20-like kinases (MSTs) and Mps one binder (MOB) 1. Okadaic acid (OA), which activates MST2, facilitates the complex formation of MOB1, MST2 and NDR1 in HEK293FT cells. The in vitro biochemical study demonstrates the phosphorylation of MOB1 by MST2. The phosphorylated MOB1 alone is capable to partially activate NDR1 in vitro, but MST2 is also required for the full activation. The knockdown of MOB1 or MST2 abolishes the OA-induced NDR1 activation in HEK293FT cells. Among MOB1 mutants, in which each serine or threonine residue is replaced with alanine, MOB1 T74A and T181A mutants fail to activate NDR1. Thr74, but not Thr181, is phosphorylated by MST2 in vitro, although MOB1 is also phosphorylated by MST2 at other site(s). The interaction of MOB1 T74A with NDR1 is barely enhanced by OA treatment. These findings indicate that the phosphorylation of MOB1 at Thr74 by MST2 is essential to make a complex of MOB1, MST2 and NDR1, and to fully activate NDR1.

Synaptic Scaffolding Molecule α Is a Scaffold To Mediate N-Methyl-d-Aspartate Receptor-Dependent RhoA Activation in Dendrites

ABSTRACT Synaptic scaffolding molecule (S-SCAM) interacts with a wide variety of molecules at excitatory and inhibitory synapses. It comprises three alternative splicing variants, S-SCAMα, -β, and -γ. We generated mutant mice lacking specifically S-SCAMα. S-SCAMα-deficient mice breathe and feed normally but die within 24 h after birth. Primary cultured hippocampal neurons from mutant mice have abnormally elongated dendritic spines. Exogenously expressed S-SCAMα corrects this abnormal morphology, while S-SCAMβ and -γ have no effect. Active RhoA decreases in cortical neurons from mutant mice. Constitutively active RhoA and ROCKII shift the length of dendritic spines toward the normal level, whereas ROCK inhibitor (Y27632) blocks the effect by S-SCAMα. S-SCAMα fails to correct the abnormal spine morphology under the treatment of N-methyl-d-aspartate (NMDA) receptor inhibitor (AP-5), Ca2+/calmodulin kinase inhibitor (KN-62), or tyrosine kinase inhibitor (PP2). NMDA treatment increases active RhoA in dendrites in wild-type hippocampal neurons, but not in mutant neurons. The ectopic expression of S-SCAMα, but not -β, recovers the NMDA-responsive accumulation of active RhoA in dendrites. Phosphorylation of extracellular signal-regulated kinase 1/2 and Akt and calcium influx in response to NMDA are not impaired in mutant neurons. These data indicate that S-SCAMα is a scaffold required to activate RhoA protein in response to NMDA receptor signaling in dendrites.

A combination of TERT promoter mutation and MGMT methylation status predicts clinically relevant subgroups of newly diagnosed glioblastomas

The prognostic impact of TERT mutations has been controversial in IDH-wild tumors, particularly in glioblastomas (GBM). The controversy may be attributable to presence of potential confounding factors such as MGMT methylation status or patients’ treatment. This study aimed to evaluate the impact of TERT status on patient outcome in association with various factors in a large series of adult diffuse gliomas. We analyzed a total of 951 adult diffuse gliomas from two cohorts (Cohort 1, n = 758; Cohort 2, n = 193) for IDH1/2, 1p/19q, and TERT promoter status. The combined IDH/TERT classification divided Cohort 1 into four molecular groups with distinct outcomes. The overall survival (OS) was the shortest in IDH wild-type/TERT mutated groups, which mostly consisted of GBMs (P < 0.0001). To investigate the association between TERT mutations and MGMT methylation on survival of patients with GBM, samples from a combined cohort of 453 IDH-wild-type GBM cases treated with radiation and temozolomide were analyzed. A multivariate Cox regression model revealed that the interaction between TERT and MGMT was significant for OS (P = 0.0064). Compared with TERT mutant-MGMT unmethylated GBMs, the hazard ratio (HR) for OS incorporating the interaction was the lowest in the TERT mutant-MGMT methylated GBM (HR, 0.266), followed by the TERT wild-type-MGMT methylated (HR, 0.317) and the TERT wild-type-MGMT unmethylated GBMs (HR, 0.542). Thus, patients with TERT mutant-MGMT unmethylated GBM have the poorest prognosis. Our findings suggest that a combination of IDH, TERT, and MGMT refines the classification of grade II-IV diffuse gliomas.

Roles of mammalian sterile 20-like kinase 2-dependent phosphorylations of Mps one binder 1B in the activation of nuclear Dbf2-related kinases.

Mammalian nuclear Dbf2‐related (NDR) kinases (LATS1, LATS2, NDR1 and NDR2) play a role in cell proliferation, apoptosis and morphological changes. Mammalian sterile 20‐like (MST) kinases and Mps one binder (MOB) proteins are important in the activation of NDR kinases. MOB1 is phosphorylated by MST1 and MST2 and this phosphorylation enhances the ability of MOB1 to activate NDR kinases. The phosphorylated MOB1 can be more effective as a scaffold protein to facilitate the MST‐dependent phosphorylation of NDR kinases and/or as a direct activator of NDR kinases. We previously reported that Thr74 of MOB1B is phosphorylated by MST2. Thr12 and Thr35 have also been identified as phosphorylation sites. In this study, we quantified the phosphorylation of Thr74 using the phosphorylated Thr74‐specific antibody. Thr74 is indeed phosphorylated by MST2, but the efficiency is low, suggesting that MOB1B can activate NDR kinases without the phosphorylation of Thr74. We also showed that the phosphorylated MOB1B activates NDR1 T444D and LATS2 T1041D, in which threonine residues phosphorylated by MST kinases are replaced with phosphorylation‐mimicking aspartic acid, more efficiently than the unphosphorylated MOB1B does. This finding supports that the phosphorylation of MOB1B enhances its ability as a direct activator of NDR kinases.

Exome Sequencing Identified CCER2 as a Novel Candidate Gene for Moyamoya Disease.

The etiology of Moyamoya disease (MMD) is still largely unclear, despite identification of RNF213 as the most significant susceptibility gene in East Asian patients. Following up our previous study confirming genetic heterogeneity in Japanese patients with MMD, we extensively surveyed novel candidate genes for a new perspective on the etiology of this disease. Two characteristic pedigrees without susceptibility variants in RNF213 were selected for whole-exome sequencing; 1 harbored 3 affected members, and the other included discordant monozygotic twins. In the former pedigree, 12 rare mutations in 12 genes were co-segregated with MMD. One of the most deleterious amino acid changes among these was p.T76_G80delinsPS in CCER2, which was also mutated in the latter pedigree (p.E242K), although the unaffected twin sister shared the same mutation reflecting reduced penetrance. These CCER2 mutations were predicted to promote aggregation or oligomerization of their protein product, using in silico functional analysis. Subsequent CCER2 re-sequencing in an additional 135 MMD probands identified 1 recurrent and an additional 2 in-frame insertion-deletion mutations, recurrent p.T76_G80delinsPS, p.H218_H220del, and p.E299del. Although CCER2 molecular function is not well characterized, it is a secretory protein expressed in the brain; therefore, it constitutes a potential biomarker of MMD.

Unique Angiographic Appearances of Moyamoya Disease Detected with 3-Dimensional Rotational Digital Subtraction Angiography Imaging Showing the Hemodynamic Status

BACKGROUND The aim of this study was to identify the unique morphological arterial features in patients with moyamoya disease on 3-dimensional rotational digital subtraction angiography. MATERIALS AND METHODS One hundred seven hemispheres of 58 consecutive patients with moyamoya disease that were analyzed with fused 3-dimensional images of internal carotid angiograms and vertebral angiograms that were marked with different colors were reviewed. Angiographic findings in the posterior watershed area were classified, and the utility of the classification was analyzed by comparing it with clinical presentations and quantitative hemodynamic parameters obtained with positron emission tomography. RESULTS Two unique angiographic appearances were identified. A vacant vessel appearance (no arterial inflow despite absence of cortical infarction) was observed mostly in transient ischemic attack hemispheres. In hemispheres with a vacant vessel appearance, cerebral blood flow was decreased, cerebral blood volume was increased, and mean transit time was prolonged significantly (P = .00017, P = .0061, and P = .00026, respectively). A cocktail vessel appearance (mixture of carotid and vertebral arterial flow) was most commonly observed in asymptomatic cases, as well as in ischemic hemispheres. Cerebral blood volume increased and mean transit time was prolonged significantly (P = .036 and P = .014, respectively) in hemispheres with a cocktail vessel appearance. The trend of progression in hemodynamic severity in the order of normal appearance, cocktail vessel appearance, and vacant vessel appearance in the watershed area was statistically significant. CONCLUSION Fused 3-dimensional digital subtraction angiography demonstrated unique angiographic features in the watershed area, and this represented the degree of cerebral hemodynamic impairment in moyamoya disease.

Novel and recurrent RNF213 variants in Japanese pediatric patients with moyamoya disease

Moyamoya disease is a progressive steno-occlusive condition of the main intracranial arteries that results in the compensatory formation of fragile moyamoya vessels at the base of the brain. RNF213 is the most significant susceptibility gene and is often found with the p.Arg4810Lys founder variant in East Asian patients. We identified three putatively deleterious variants of this gene from three pediatric patients: two were novel, and one was a recurrent missense variant previously reported in other pediatric patients.

Erratum to: LAPTM4B-35 is a novel prognostic factor for glioblastoma

with low LAPTM4B-35 expression should have read 16 (instead of 17). The correct Fig. 2 and caption are printed below. 3. In the Table 1, the number of LAPTM4B low patients should have read 16 (instead of 12). 4. In the Table 1, the number of LAPTM4B high patients should have read 23 (instead of 27). 5. In the Supplementary Table 1, the number of gross total resections in grade IV patients should have read 12 (27.9%), instead of 21 (48.8%). Erratum to: J Neurooncol DOI 10.1007/s11060-017-2369-0