KIF1Bβ and Neuroblastoma: Failure to Divide and Cull

Neuroblastomas are associated with KIF1Bβ mutations within tumor suppressor region 1p36. In this issue of Developmental Cell, Li et al. (2016) show that KIF1Bβ binding releases calcineurin autoinhibition, leading to dephosphorylation of the DRP1 GTPase and subsequent mitochondrial fragmentation. KIF1Bβ impairment causes mitochondrial hyperfusion, impairing developmental apoptosis and promoting tumorigenesis

An Analysis of Energy Efficient Building Principles

Student Number : 9709225V - MSc project report - School of Construction Economics and Management - Faculty of Engineering and the Built EnvironmentThis research was conducted in order to highlight the misconception that there may be a single answer to the challenges of energy efficient design; a “single elixir that will be the answer to all problems” (Holm, 1996). Existing literature pertaining to energy efficient design principles was analysed and tested against a well known example of Southern African energy efficient building practice; the Botswana Technology Centre (BOTEC). BOTEC was selected as the case study for this investigation because it was designed to be a living exhibition of energy efficient design and as such a manual or ‘elixir’ for alternate design. BOTEC was analysed on site, personal interviews were held with the architect and a questionnaire was circulated to the users of the building in order to observe whether the principles used at the BOTEC building are appropriate and represent the “single elixir, the answer to all problems,” with regard to energy efficient design (Holm, 1996). Although BOTEC appears to perform well, interviews with the users of the BOTEC building suggest that the building does not perform well in winter at all. Interviews with the architectural consultant who worked on the BOTEC building expose a simple oversight in design which leads to ‘this building’s underperformance in winter’. In concurrence with Holm therefore, this report ultimately shows that there are no perfect solutions to energy efficient design and by applying a once successful solution without taking cognisance of specific climatic and geological differences, the building will not function correctly

SPG20 protein spartin is recruited to midbodies by ESCRT-III protein Ist1 and participates in cytokinesis.

Hereditary spastic paraplegias (HSPs, SPG1-46) are inherited neurological disorders characterized by lower extremity spastic weakness. Loss-of-function SPG20 gene mutations cause an autosomal recessive HSP known as Troyer syndrome. The SPG20 protein spartin localizes to lipid droplets and endosomes, and it interacts with tail interacting protein 47 (TIP47) as well as the ubiquitin E3 ligases atrophin-1-interacting protein (AIP)4 and AIP5. Spartin harbors a domain contained within microtubule-interacting and trafficking molecules (MIT) at its N-terminus, and most proteins with MIT domains interact with specific ESCRT-III proteins. Using yeast two-hybrid and in vitro surface plasmon resonance assays, we demonstrate that the spartin MIT domain binds with micromolar affinity to the endosomal sorting complex required for transport (ESCRT)-III protein increased sodium tolerance (Ist)1 but not to ESCRT-III proteins charged multivesicular body proteins 1-7. Spartin colocalizes with Ist1 at the midbody, and depletion of Ist1 in cells by small interfering RNA significantly decreases the number of cells where spartin is present at midbodies. Depletion of spartin does not affect Ist1 localization to midbodies but markedly impairs cytokinesis. A structure-based amino acid substitution in the spartin MIT domain (F24D) blocks the spartin-Ist1 interaction. Spartin F24D does not localize to the midbody and acts in a dominant-negative manner to impair cytokinesis. These data suggest that Ist1 interaction is important for spartin recruitment to the midbody and that spartin participates in cytokinesis

Editorial: Hereditary Spastic Paraplegias: At the Crossroads of Molecular Pathways and Clinical Options.

International audienc

Clinical Trial Designs and Measures in Hereditary Spastic Paraplegias

Hereditary spastic paraplegias (HSPs) are a large group of genetically-diverse neurologic disorders characterized clinically by a common feature of lower extremity spasticity and gait difficulties. Current therapies are predominantly symptomatic, and even then usually provide inadequate relief of symptoms. Going forward, HSP therapeutics development requires a systematic analysis of quantifiable measures and tools to assess treatment response. This review summarizes promising therapeutic targets, assessment measures, and previous clinical trials for the HSPs. Oxidative stress, signaling pathways, microtubule dynamics, and gene rescue/replacement have been proposed as potential treatment targets or modalities. Quantitative evaluation of pre-clinical rodent HSP models emphasize rotarod performance, foot base angle, grip strength, stride length, beam walking, critical speed, and body weight. Clinical measures of HSP in humans include 10-m gait velocity, the Spastic Paraplegia Rating Scale (SPRS), Ashworth Spasticity Scale, Fugl-Meyer Scale, timed up-and-go, and the Gillette Functional Assessment Questionnaire. We conducted a broad search for past clinical trials in HSPs and identified trials that investigated pharmacological agents including atorvastatin, gabapentin, L-threonine, botulinum toxin, dalfampridine, methylphenidate, and baclofen. We provide recommendations for future HSP treatment directions based on these prior research experiences as well as regulatory insight

Clueless/CLUH regulates mitochondrial fission by promoting recruitment of Drp1 to mitochondria

Mitochondrial fission is critically important for controlling mitochondrial morphology, function, quality and transport. Drp1 is the master regulator driving mitochondrial fission, but exactly how Drp1 is regulated remains unclear. Here, we identified Drosophila Clueless and its mammalian orthologue CLUH as key regulators of Drp1. As with loss of drp1, depletion of clueless or CLUH results in mitochondrial elongation, while as with drp1 overexpression, clueless or CLUH overexpression leads to mitochondrial fragmentation. Importantly, drp1 overexpression rescues adult lethality, tissue disintegration and mitochondrial defects of clueless null mutants in Drosophila. Mechanistically, Clueless and CLUH promote recruitment of Drp1 to mitochondria from the cytosol. This involves CLUH binding to mRNAs encoding Drp1 receptors MiD49 and Mff, and regulation of their translation. Our findings identify a crucial role of Clueless and CLUH in controlling mitochondrial fission through regulation of Drp1

SUMOylation of the mitochondrial fission protein Drpl occurs at multiple nonconsensus sites within the B domain and is linked to its activity cycle

Dynamin‐related protein (Drp) 1 is a key regulator of mitochondrial fission and is composed of GTP‐binding, Middle, insert B, and C‐terminal GTPase effector (GED) domains. Drpl associates with mitochondrial fission sites and promotes membrane constriction through its intrinsic GTPase activity. The mechanisms that regulate Drpl activity remain poorly understood but are likely to involve reversible post‐translational modifications, such as conjugation of small ubiquitin‐like modifier (SUMO) proteins. Through a detailed analysis, we find that Drpl interacts with the SUMO‐conjugating enzyme Ubc9 via multiple regions and demonstrate that Drpl is a direct target of SUMO modification by all three SUMO isoforms. While Drpl does not harbor consensus SUMOylation sequences, our analysis identified2 clusters of lysine residues within the B domain that serve as noncanonical conjugation sites. Although initial analysis indicates that mitochondrial recruitment of ectopically expressed Drpl in response to staurosporine is unaffected by loss of SUMOylation, we find that Drpl SUMOylation is enhanced in the context of the K38A mutation. This dominant‐negative mutant, which is deficient in GTP binding and hydrolysis, does not associate with mitochondria and prevents normal mitochondrial fission. This finding suggests that SUMOylation of Drpl is linked to its activity cycle and is influenced by Drpl localization.—Figueroa‐Romero, C., Iniguez‐Lluhi, J. A., Stadler, J., Chang, C.‐R., Arnoult, D., Keller, P. J., Hong, Y., Blackstone, C., Feldman, E. L. SUMOylation of the mitochondrial fission protein Drpl occurs at multiple nonconsensus sites within the B domain and is linked to its activity cycle. FASEB J. 23, 3917–3927 (2009). www.fasebj.orgPeer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/154272/1/fsb2fj09136630.pd

Lysosomal abnormalities in hereditary spastic paraplegia types SPG15 and SPG11

Objective Hereditary spastic paraplegias (HSPs) are among the most genetically diverse inherited neurological disorders, with over 70 disease loci identified (SPG1-71) to date. SPG15 and SPG11 are clinically similar, autosomal recessive disorders characterized by progressive spastic paraplegia along with thin corpus callosum, white matter abnormalities, cognitive impairment, and ophthalmologic abnormalities. Furthermore, both have been linked to early-onset parkinsonism. Methods We describe two new cases of SPG15 and investigate cellular changes in SPG15 and SPG11 patient-derived fibroblasts, seeking to identify shared pathogenic themes. Cells were evaluated for any abnormalities in cell division, DNA repair, endoplasmic reticulum, endosomes, and lysosomes. Results Fibroblasts prepared from patients with SPG15 have selective enlargement of LAMP1-positive structures, and they consistently exhibited abnormal lysosomal storage by electron microscopy. A similar enlargement of LAMP1-positive structures was also observed in cells from multiple SPG11 patients, though prominent abnormal lysosomal storage was not evident. The stabilities of the SPG15 protein spastizin/ZFYVE26 and the SPG11 protein spatacsin were interdependent. Interpretation Emerging studies implicating these two proteins in interactions with the late endosomal/lysosomal adaptor protein complex AP-5 are consistent with shared abnormalities in lysosomes, supporting a converging mechanism for these two disorders. Recent work withZfyve26−/− mice revealed a similar phenotype to human SPG15, and cells in these mice had endolysosomal abnormalities. SPG15 and SPG11 are particularly notable among HSPs because they can also present with juvenile parkinsonism, and this lysosomal trafficking or storage defect may be relevant for other forms of parkinsonism associated with lysosomal dysfunction

Complicated spastic paraplegia in patients with AP5Z1 mutations (SPG48)

Objective: Biallelic mutations in the AP5Z1 gene encoding the AP-5 ζ subunit have been described in a small number of patients with hereditary spastic paraplegia (HSP) (SPG48); we sought to define genotype–phenotype correlations in patients with homozygous or compound heterozygous sequence variants predicted to be deleterious. Methods: We performed clinical, radiologic, and pathologic studies in 6 patients with biallelic mutations in AP5Z1. Results: In 4 of the 6 patients, there was complete loss of AP-5 ζ protein. Clinical features encompassed not only prominent spastic paraparesis but also sensory and motor neuropathy, ataxia, dystonia, myoclonus, and parkinsonism. Skin fibroblasts from affected patients tested positive for periodic acid Schiff and autofluorescent storage material, while electron microscopic analysis demonstrated lamellar storage material consistent with abnormal storage of lysosomal material. Conclusions: Our findings expand the spectrum of AP5Z1-associated neurodegenerative disorders and point to clinical and pathophysiologic overlap between autosomal recessive forms of HSP and lysosomal storage disorders