Epidermal growth factor receptor (EGFR) has been detected in the nucleus in many tissues and cell lines. However, the potential functions of nuclear EGFR have largely been overlooked. Here we demonstrate that nuclear EGFR is strongly correlated with highly proliferating activities of tissues. When EGFR was fused to the GAL4 DNA-binding domain, we found that the carboxy terminus of EGFR contained a strong transactivation domain. Moreover, the receptor complex bound and activated AT-rich consensus-sequence-dependent transcription, including the consensus site in cyclin D1 promoter. By using chromatin immunoprecipitation assays, we further demonstrated that nuclear EGFR associated with promoter region of cyclin D1 in vivo. EGFR might therefore function as a transcription factor to activate genes required for highly proliferating activities.
We identified a human homolog of Drosophila warts tumor suppressor gene, termed h-warts, which was mapped at chromosome 6q24-25.1. The h-warts protein has a serine/ threonine kinase domain and is localized to centrosomes in interphase cells. However, it becomes localized to the mitotic apparatus, including spindle pole bodies, mitotic spindle, and midbody, in a highly dynamic manner during mitosis. Furthermore, h-warts is specifically phosphorylated in cells at mitotic phase, most likely by Cdc2 kinase. These findings suggest that hwarts functions as a component of the mitotic apparatus and is involved in proper progression of mitosis.z 1999 Federation of European Biochemical Societies.
NE-dlg/SAP102, a neuronal and endocrine tissue-specific membrane-associated guanylate kinase family protein, is known to bind to C-terminal ends of N-methyl-Daspartate receptor 2B (NR2B) through its PDZ (PSD-95/ Dlg/ZO-1) domains. NE-dlg/SAP102 and NR2B colocalize at synaptic sites in cultured rat hippocampal neurons, and their expressions increase in parallel with the onset of synaptogenesis. We have identified that NE-dlg/ SAP102 interacts with calmodulin in a Ca 2؉ -dependent manner. The binding site for calmodulin has been determined to lie at the putative basic ␣-helix region located around the src homology 3 (SH3) domain of NE-dlg/ SAP102. Using a surface plasmon resonance measurement system, we detected specific binding of recombinant NE-dlg/SAP102 to the immobilized calmodulin with a K d value of 44 nM. However, the binding of Ca 2؉ /calmodulin to NE-dlg/SAP102 did not modulate the interaction between PDZ domains of NE-dlg/SAP102 and the C-terminal end of rat NR2B. We have also identified that the region near the calmodulin binding site of NE-dlg/ SAP102 interacts with the GUK-like domain of PSD-95/ SAP90 by two-hybrid screening. Pull down assay revealed that NE-dlg/SAP102 can interact with PSD-95/ SAP90 in the presence of both Ca 2؉ and calmodulin. These findings suggest that the Ca 2؉ /calmodulin modulates interaction of neuronal membrane-associated guanylate kinase proteins and regulates clustering of neurotransmitter receptors at central synapses.Over the past decades, many efforts were given to identify the various proteins composing the postsynaptic sites in neurons. Postsynaptic densities (PSDs), 1 which are the insoluble fractions of neurons in traditional biochemical detergents, have been found to contain cytoskeletal proteins and their associated proteins, such as actin (1), spectrin, tubulin, microtubule-associated proteins (2), calmodulin (3), and calmodulin-dependent protein kinase II (4). Isolated PSDs have also been shown to be enriched in N-methyl-D-aspartate (NMDA) and ␣-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid receptors. Recently, several proteins, including PSD-95/SAP90 (5), NE-dlg/SAP102 (6, 7), and chapsyn-110/PSD-93 (8), which belong to a novel protein family called membrane-associated guanylate kinases (MAGUKs), have been identified as components of PSD. These MAGUK proteins are homologous to the Drosophila disc large (dlg) tumor suppressor protein (6, 7) in both sequence and structural organization and contain three distinct domains: an N-terminal segment comprising one or three copies of 80 -90 amino acid motif called PDZ (PSD-95/Dlg/ZO-1) domain, a src homology 3 (SH3) domain, and a region with high similarity to guanylate kinases (9, 10). These domains have been shown to be utilized as modules for interacting with various cellular proteins.PSD-95/SAP90 has been reported to have an activity of clustering shaker-type K ϩ channels (11) and NMDA receptor 2B (NR2B) (12). The PDZ domains of PSD-95/SAP90 were found to interact with the C terminus (Ser/Thr)-X-Val ((S/T)XV) m...
Among adult patients with supratentorial GBM, female sex and histopathological characteristics consistent with giant cell GBM may be predictive of a better survival rate, as may traditional factors (that is, younger age, good KPS score, more aggressive resection, and a long progression-free interval).
We have cloned a cDNA for a novel human homolog of the Drosophila discs large (dlg) tumor suppressor protein, termed NE-dlg (neuronal and endocrine dlg). Northern blot analysis revealed that the gene is highly expressed in neuronal and endocrine tissues. Fluorescence in situ hybridization (FISH) and radiation hybrid mapping studies localized the NE-dlg gene to chromosome Xq13. We also found that the NE-dlg gene encoded a 100 kDa protein. Immunolocalization studies using an NE-dlg antibody showed that the protein tended to be expressed in non-proliferating cells, such as neurons, cells in Langerhans islets of the pancreas, myocytes of the heart muscles, and the prickle and functional layer cells of the esophageal epithelium. Proliferative cells, including various cultured cancer cell lines and basal cells in the esophageal epithelium, showed little expression of the NE-dlg protein. In addition, yeast two-hybrid screening and in vitro binding assays revealed that the NE-dlg interacted with the carboxyl-terminal region of the APC tumor suppressor protein. These data suggest that NE-dlg negatively regulates cell proliferation through its interaction with the APC protein.
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