Cerebral cavernous malformation is a common human vascular disease that arises due to loss-of-function mutations in genes encoding

In the central nervous system, clathrin-mediated endocytosis is crucial for efficient synaptic transmission. Clathrin-coated vesicle assembly and disassembly is regulated by some 30 adaptor and accessory proteins, most of which interact with clathrin heavy chain. Using the calcyon cytosolic domain as bait, we isolated clathrin light chain in a yeast two-hybrid screen. The interaction domain was mapped to the heavy chain binding domain and C-terminal regions of light chain. Further, the addition of the calcyon C terminus stimulated clathrin self-assembly in a dose-dependent fashion. Calcyon, which is a single transmembrane protein predominantly expressed in brain, localized to vesicular compartments within preand postsynaptic structures. There was a high degree of overlap in the distribution of LC and calcyon in neuronal dendrites, spines, and cell bodies. Co-immunoprecipitation studies further suggested an association of calcyon with the clathrin-mediated endocytic machinery. Compared with controls, HEK293 cells overexpressing calcyon exhibited significantly enhanced transferrin uptake but equivalent levels of recycling. Conversely, transferrin uptake was largely abolished in neocortical neurons obtained from mice homozygous for a calcyon null allele, whereas recycling proceeded at wild type levels. Collectively, these data indicate a role for calcyon in clathrin-mediated endocytosis in brain.In the central nervous system, clathrin-mediated endocytosis (CME) 3 is essential for pre-and postsynaptic adaptations correlated with learning and memory (1-4). In axon terminals, CME is required for synaptic vesicle recycling, a process linked to optimizing levels of releasable pools of neurotransmitter during synaptic activity (4). Similarly, in dendritic spines, internalization of postsynaptic receptors via clathrin-coated vesicles (CCVs) plays a role in long term changes in synaptic strength (2, 5-7). The protein backbone of CCVs consists of clathrin triskelions assembled into a lattice structure. Each triskelion is composed of three heavy chains (HCs) and three light chains (LCs). The time and place of CCV assembly and breakdown are regulated by some 30 adaptor and accessory proteins (8), most of which are ubiquitous and interact with HC. In contrast to HC, only four proteins aside from HC are known to interact with LC, including calmodulin (9), Hsc70 (heat shock protein 70) (10), Hip1 (Huntingtin-interacting protein 1), and the closely related protein Hip1R (Hip1-related protein) (11-14). However, targeted deletion studies indicate that neuronal enriched isoforms of several adaptor and accessory proteins are essential for optimal synaptic transmission (4). The enrichment of Hip1 and calmodulin in neurons raises the possibility that adaptor and accessory protein interactions with LC might likewise be crucial determinants of efficient CME in the central nervous system.Calcyon is a single transmembrane protein predominantly expressed in the central nervous system and localized to membranous intracellular compartments wi...

Frontotemporal lobar degeneration with TDP- 43 inclusions (FTLD-TDP) is characterized by progressive decline in behavior, executive function, and language. Progranulin (GRN) gene mutations are pathogenic for FTLD-TDP, and GRN transcript haploinsufficiency is the proposed disease mechanism. However, the evidence for this hypothesis comes mainly from blood-derived cells; we measured progranulin expression in brain. We characterized mRNA and protein levels of progranulin from four brain regions (frontal cortex, temporal cortex, occipital cortex, and cerebellum) in FTLD-TDP patients with and without GRN mutations, as well as neurologically normal individuals. Moreover, we performed immunohistochemistry to evaluate the degree of TDP-43 pathology and microglial infiltration present in these groups. In most brain regions, patients with GRN mutations showed mRNA levels comparable to normal controls and to FTLD-TDP without GRN mutations. However, GRN transcript levels in a brain region severely affected by disease (frontal cortex) were increased in mutation-bearing patients. When compared with normal individuals, GRN mutation-bearing cases had a significant reduction in the amount of progranulin protein in the cerebellum and occipital cortex, but not in the frontal and temporal cortices. In GRN mutant cases, GRN mRNA originated from the normal allele, and moderate microglial infiltration was observed. In conclusion, GRN mutation carriers have increased levels of mRNA transcript from the normal allele in brain, and proliferation of microglia likely increases progranulin levels in affected regions of the FTLD-TDP brain, and whether or not these findings underlie the accumulation of TDP-43 pathology in FTLD-TDP linked to GRN mutations remains to be determined.

Background Nuclear factor IA (NFIA), a transcription factor and essential regulator in embryonic glial development, is highly expressed in human glioblastoma (GBM) compared with normal brain, but its contribution to GBM and cancer pathogenesis is unknown. Here we demonstrate a novel role for NFIA in promoting growth and migration of GBM and establish the molecular mechanisms mediating these functions. Methods To determine the role of NFIA in glioma, we examined the effects of NFIA in growth, proliferation, apoptosis, and migration. We used gain-of-function (overexpression) and loss-of-function (shRNA knockdown) of NFIA in primary patient-derived GBM cells and established glioma cell lines in culture and in intracranial xenografts in mouse brains. Results Knockdown of native NFIA blocked tumor growth and induced cell death and apoptosis. Complementing this, NFIA overexpression accelerated growth, proliferation, and migration of GBM in cell culture and in mouse brains. These NFIA tumor-promoting effects were mediated via transcriptional repression of p53, p21, and plasminogen activator inhibitor 1 (PAI1) through specific NFIA-recognition sequences in their promoters. Importantly, the effects of NFIA on proliferation and apoptosis were independent of TP53 mutation status, a finding especially relevant for GBM, in which TP53 is frequently mutated. Conclusion NFIA is a modulator of GBM growth and migration, and functions by distinct regulation of critical oncogenic pathways that govern the malignant behavior of GBM.