Photoreceptor phagosome processing defects and disturbed autophagy in retinal pigment epithelium of Cln3Δex1-6 mice modelling juvenile neuronal ceroid lipofuscinosis (Batten disease)

Retinal degeneration and visual impairment are the first signs of juvenile neuronal ceroid lipofuscinosis caused by CLN3 mutations, followed by inevitable progression to blindness. We investigated retinal degeneration in Cln3Δex1-6 null mice, revealing classic ‘fingerprint’ lysosomal storage in the retinal pigment epithelium (RPE), replicating the human disease. The lysosomes contain mitochondrial F0-ATP synthase subunit c along with undigested membranes, indicating a reduced degradative capacity. Mature autophagosomes and basal phagolysosomes, the terminal degradative compartments of autophagy and phagocytosis, are also increased in Cln3Δex1-6 RPE, reflecting disruption to these key pathways that underpin the daily phagocytic turnover of photoreceptor outer segments (POS) required for maintenance of vision. The accumulated autophagosomes have post-lysosome fusion morphology, with undigested internal contents visible, while accumulated phagosomes are frequently docked to cathepsin D-positive lysosomes, without mixing of phagosomal and lysosomal contents. This suggests lysosome-processing defects affect both autophagy and phagocytosis, supported by evidence that phagosomes induced in Cln3Δex1-6-derived mouse embryonic fibroblasts have visibly disorganized membranes, unprocessed internal vesicles and membrane contents, in addition to reduced LAMP1 membrane recruitment. We propose that defective lysosomes in Cln3Δex1-6 RPE have a reduced degradative capacity that impairs the final steps of the intimately connected autophagic and phagocytic pathways that are responsible for degradation of POS. A build-up of degradative organellar by-products and decreased recycling of cellular materials is likely to disrupt processes vital to maintenance of vision by the RPE

Multiple myeloma presenting as an intracranial plasmacytoma: a case report

Multiple myeloma presenting as an intracranial tumor (plasmacytoma) is very rare. An 81-year-old woman was admitted to our hospital because of gait disturbance. A blood laboratory test revealed a mildly increased lactate dehydrogenase (236 IU/L) and glucose (121 mg/dl). Blood protein fractions were normal. Brain computed tomography and magnetic resonance imaging revealed an intracranial mass (5 × 4 × 3 cm) in the brain base next to the clavus, and it was clinically diagnosed as chordoma. An excision of the brain tumor was performed. Imaging modalities including ultrasound, x-ray, computed tomography, magnetic resonance imaging and positron emission tomography did not reveal any tumors other than the brain tumor. The tumor was soft, fragile, and bloody. Microscopically, a monotonous proliferation of atypical plasma cells with hyperchromatic nuclei was recognized. Histochemically, the tumor cells were pyroninophilic and the congo-red stain revealed amyloidosis. Immunohistochemically, the tumor cells were positive for κ-chain and negative for cytokeratin, epithelial membrane antigen, vimentin, CD45, CD20, CD45RO, λ-chain, IgM, IgA, IgG, synaptophysin, chromogranin, S100 protein, desmin, α-smooth muscle antigen, myoglobin, p53 protein, and glial fibrillary acidic protein. The Ki-67 labeling was 11%. Intracranial plasmacytoma was pathologically diagnosed. The patient was treated by adjuvant chemoradiation, and entered into the complete remission stage. However, multiple metastases emerged in the vertebral bones and ribs six months after the remission. A diagnosis of multiple myeloma was made. The urine revealed Bence-Jones protein of monoclonal IgG κ-chain type, but blood M protein was not recognized. The patient's condition gradually deteriorated. The patient died of respiratory failure due to bronchopneumonia 18 months after the admission. The present case indicates that multiple myeloma may manifest as an intracranial brain tumor (plasmacytoma)

Cerebellar ataxia and sensory ganglionopathy associated with light-chain myeloma.

BACKGROUND: Cerebellar ataxia with sensory ganglionopathy is a rare neurological combination that can occur in some hereditary ataxias including mitochondrial diseases and in gluten sensitivity. Individually each condition can be a classic paraneoplastic neurological syndrome. We report a patient with this combination who was diagnosed with light-chain myeloma ten years after initial presentation. CASE PRESENTATION: A 65-year-old Caucasian lady was referred to our Ataxia Clinic because of a 6-year history of progressive unsteadiness and a 2-year history of slurred speech. Past medical history included arterial hypertension. The patient was a non-smoker was not consuming alcohol excessively. There was no family history of ataxia. Neurological examination revealed prominent gaze-evoked nystagmus, heel to shin ataxia, gait ataxia, reduced reflexes and loss of vibration sensation in the legs. Cerebellar ataxia was confirmed using magnetic resonance spectroscopy of the cerebellum and sensory ganglionopathy using neurophysiological assessments including blink reflex study. A muscle biopsy that was arranged to explore the possibility of mitochondrial disease revealed amyloidosis. Urinalysis confirmed the presence of light chains. A bone marrow biopsy confirmed the diagnosis of light chain multiple myeloma. CONCLUSIONS: Whilst it could be argued that this could simply be a coincidence, the rarity of these conditions and the absence of an alternative aetiology for the neurological dysfunction argue in favour of a paraneoplastic phenomenon

Flat Clathrin Lattices: stable features of the plasma membrane

Clathrin-mediated endocytosis (CME) is a fundamental property of eukaryotic cells. Classical CME proceeds via the formation of clathrin-coated pits (CCP) at the plasma membrane that invaginate to form clathrin-coated vesicles; a process that is well understood. However, clathrin also assembles into flat clathrin lattices (FCL); these structures remain poorly described and their contribution to cell biology is unclear. We have used quantitative imaging to provide the first comprehensive description of FCL and explore their influence on plasma membrane organization. Ultrastructural analysis by electron and super-resolution microscopy revealed two discrete populations of clathrin structures. CCP were typified by their sphericity, small size and homogeneity. FCL were planar, large and heterogeneous, and present on both the dorsal and ventral surfaces of cells. Live microscopy demonstrated that CCP are short-lived and culminate in a peak of dynamin recruitment, consistent with classical CME. In contrast, FCL were long-lived with sustained association with dynamin. We investigated the biological relevance of FCL using the chemokine receptor CCR5 as a model system. Agonist activation leads to sustained recruitment of CCR5 to FCL. Quantitative molecular imaging indicated that FCL partitioned receptors at the cell surface. Our observations suggest that FCL provide stable platforms for the recruitment of endocytic cargo

Effects of free convection currents on the oscillatory flow of an electrically conducting fluid past a stationary or steadily moving vertical plate with variable suction and constant heat flux

An approximate analysis of a two-dimensional flow of an electrically conducting incompressible viscous fluid past an infinite porous plate, stationary or steadily moving in its own plane, is presented under the following conditions: i) suction velocity oscillates about a constant non-zero mean; ii) the free stream velocity oscillating in time about a constant mean; iii) constant heat flux at the plate; iv) presence of free convection currents due to the temperature difference; v) a uniform transverse magnetic field. Approximate solutions to coupled nonlinear equations governing the problem have been derived for the transient velocity, the transient temperature, the amplitude and the phase of the skin-friction and the Nusselt number. During the course of analysis, the effects of the Grashof number Gr, the magnetic field parameter M, the suction parameter A, the Eckert number E, the velocity of the plate V and the frequency 'omega' have been discussed

Agonist-induced endocytosis of CC chemokine receptor 5 is clathrin dependent

The signaling activity of several chemokine receptors, including CC chemokine receptor 5 (CCR5), is in part controlled by their internalization, recycling, and/or degradation. For CCR5, agonists such as the chemokine CCL5 induce internalization into early endosomes containing the transferrin receptor, a marker for clathrin-dependent endocytosis, but it has been suggested that CCR5 may also follow clathrin-independent routes of internalization. Here, we present a detailed analysis of the role of clathrin in chemokine-induced CCR5 internalization. Using CCR5-transfected cell lines, immunofluorescence, and electron microscopy, we demonstrate that CCL5 causes the rapid redistribution of scattered cell surface CCR5 into large clusters that are associated with flat clathrin lattices. Invaginated clathrin-coated pits could be seen at the edge of these lattices and, in CCL5-treated cells, these pits contain CCR5. Receptors internalized via clathrin-coated vesicles follow the clathrin-mediated endocytic pathway, and depletion of clathrin with small interfering RNAs inhibits CCL5-induced CCR5 internalization. We found no evidence for CCR5 association with caveolae during agonist-induced internalization. However, sequestration of cholesterol with filipin interferes with agonist binding to CCR5, suggesting that cholesterol and/or lipid raft domains play some role in the events required for CCR5 activation before internalization