Neurofibromatosis Type 1 (NF1) Tumor Suppressor, Neurofibromin, Regulates the Neuronal Differentiation of PC12 Cells via Its Associating Protein, CRMP-2 (original) (raw)
Related papers
Journal of Investigative Dermatology, 2000
suppressor gene product, neurofibromin, functions in part as a Ras-GAP, a negative regulator of Ras. Neurofibromin is implicated in the neuronal abnormality of NF1 patients; however, the precise cellular function of neurofibromin has yet to be clarified. Using proteomic strategies, we identified a set of neurofibromin-associating cellular proteins, including axon regulator Collapsin response mediator protein-2 (CRMP-2). CRMP-2 directly bound to the C-terminal domain of neurofibromin, and this association was regulated by the manner of CRMP-2 phosphorylation. In nerve growth factor (NGF)-stimulated PC12 cells, neurofibromin and CRMP-2 co-localized particularly on the distal tips and branches of extended neurites. Suppression of neurofibromin using NF1 siRNA significantly inhibited this neurite outgrowth and upregulated a series of CRMP-2 phosphorylations by kinases identified as CDK5, GSK-3b and Rho-kinase (RhoK).
RAS and beyond: the many faces of the neurofibromatosis type 1 protein
Disease Models & Mechanisms, 2022
Neurofibromatosis type 1 is a rare neurogenetic syndrome, characterized by pigmentary abnormalities, learning and social deficits, and a predisposition for benign and malignant tumor formation caused by germline mutations in the NF1 gene. With the cloning of the NF1 gene and the recognition that the encoded protein, neurofibromin, largely functions as a negative regulator of RAS activity, attention has mainly focused on RAS and canonical RAS effector pathway signaling relevant to disease pathogenesis and treatment. However, as neurofibromin is a large cytoplasmic protein the RAS regulatory domain of which occupies only 10% of its entire coding sequence, both canonical and non-canonical RAS pathway modulation, as well as the existence of potential non-RAS functions, are becoming apparent. In this Special article, we discuss our current understanding of neurofibromin function.
Molecular and Cellular Biology, 1993
Sequence analysis has shown significant homology between the catalytic regions of the mammalian ras GTPase-activating protein (GAP), yeast Ira1p and Ira2p (inhibitory regulators of the RAS-cyclic AMP pathway), and neurofibromin, the protein encoded by the NF1 gene. Yeast expression experiments have confirmed that a 381-amino-acid segment of neurofibromin, dubbed the GAP-related domain (GRD), can function as a GAP. Using the RNA polymerase chain reaction with primers flanking the NF1-GRD, we have identified evidence for alternative splicing in this region of the NF1 gene. In addition to the already published sequence (type I), an alternative RNA carrying a 63-nucleotide insertion (type II) is present in all tissues examined, although the relative amounts of types I and II vary. The insertion is conserved across species but is not present in GAP, IRA1, or IRA2. GenBank searches have failed to identify significant similarity between the inserted sequence and known DNA or protein sequen...
2019
Neurofibromin is the protein product of the NF1 gene which is mutated in the Rasopathy disease Neurofibromatosis Type I. Defects in NF1 lead to aberrant signaling through the RAS-MAPK pathway due to disruption of the Neurofibromin GTPase-activating function on RAS family small GTPases. Very little is known about the function of the majority of Neurofibromin; to date, biochemical and structural data exist only for the GAP domain and the region containing a Sec-PH motif. To better understand the role of this large protein, we carried out a series of biochemical and biophysical studies which demonstrate that full length Neurofibromin forms a high-affinity dimer. Neurofibromin dimerization also occurs in cells, and likely has biological and clinical implications. Analysis of purified full-length and truncated variants of Neurofibromin by negative stain electron microscopy reveals the overall architecture of the dimer and predicts the potential interactions which contribute to the dimer ...
Journal of Biological Chemistry, 1995
The neurofibromatosis type 1 (NF1) gene encodes a protein, neurofibromin, containing GTPase-activating protein-related domain (GRD) that stimulates intrinsic GTPase activity of Ras protein. By screening a randomly mutagenized NF1-GRD library in Saccharomyces cerevisiae, we isolated two NF1-GRD mutants (NF201 and NF204) with single amino acid substitutions, which suppress the heat shock-sensitive phenotype of the RAS2(G19V) mutant. The NF1-GRD mutants also suppress the oncogenic Ras-induced transformation of NIH 3T3 mouse fibroblasts (Nakafuku, M.
An anti-Ras function of neurofibromatosis type 2 gene product (NF2/Merlin)
The Journal of biological chemistry, 1994
Previously, we have cloned a candidate for the 595-amino acid neurofibromatosis type 2 tumor suppressor called NF2 or Merlin, with striking sequence similarity in its N-terminal half to an F-actin-binding protein family called TERM, which includes talin, ezrin, radixin, and moesin (Trofatter, J. A., MacCollin, M. M., Rutter, J. L., Murrell, J. R., Duyao, M. P., Parry, D. M., Eldridge, R., Kley, N., Menon, A. G., Pulaski, K., Haase, V. H., Ambrose, C. M., Munro, D., Bove, C., Haines, J. L., Martuza, R. L., MacDonald, M. E., Seizinger, B. R., Short, M. P., Buckler, A. J., and Gusella, J. F. (1993) Cell 72, 791-800). In an attempt to determine whether NF2 serves as a tumor suppressor and if so whether its N-terminal half is involved in its anti-oncogenicity, both full-length NF2 and its N-terminal half (NF2-N, residues 9-359) have been expressed in v-Ha-Ras-transformed NIH/3T3 cells. Like neurofibromatosis type 1 (NF1) fragments (Nur-E-Kamal, M. S. A., Varga, M., and Maruta, H. (1993) ...
Journal of Cellular Biochemistry, 2009
Mapping and chemical characterization of post-translational modifications (PTMs) in proteins are critical to understand the regulatory mechanisms involving modified proteins and their role in disease. Neurofibromatosis type 1 (NF-1) is an autosomal dominantly inherited disorder, where NF1 mutations usually result in a reduced level of the tumor suppressor protein, neurofibromin (NF). NF is a multifunctional cytoplasmic protein that regulates microtubule dynamics and participates in several signaling pathways, particularly the RAS signaling pathway. NF is a Ras GTPase-activating protein (GAP) that prevents oncogenesis by converting GTP-Ras to GDP-Ras. This function of NF is regulated by phosphorylation. Interplay of phosphorylation with O-GlcNAc modification on the same or vicinal Ser/Thr residues, the Yin Yang sites, is well known in cytoplasmic and nuclear proteins. The dynamic aspects of PTMs and their interplay being difficult to follow in vivo, we undertook this in silico work to predict and define the possible role of Yin Yang sites in NF-1. Interplay of phosphorylation and O-GlcNAc modification is proposed as a mechanism controlling the Ras signaling pathway.
Molecular and Cellular Biology, 1996
Neurofibromin plays a critical role in the downregulation of Ras proteins in neurons and Schwann cells. Thus, the ability of neurofibromin to interact with Ras is crucial for its function, as mutations in NF1 that abolish this interaction fail to maintain function. To investigate the neurofibromin-Ras interaction in a systematic manner, we have carried out a yeast two-hybrid screen using a mutant of H-ras, H-rasD92K, defective for interaction with the GTPase-activated protein-related domain (GRD) of NF1. Two screens of a randomly mutagenized NF1-GRD library led to the identification of seven novel NF1 mutants. Characterization of the NF1-GRD mutants revealed that one class of mutants are allele specific for H-raSD92K. These mutants exhibit increased affinity for H-raSD92K and significantly reduced affinity for wild-type H-ras protein. Furthermore, they do not interact with another H-ras mutant defective for interaction with GTPase-activating proteins. Another class of mutants are hi...
Proceedings of the National Academy of Sciences, 1993
The NFI gene, which is altered in patients with type 1 neurofibromatosis, encodes neurofibromin, a protein whose GTPase-activating function can negatively regulate GTP Ras by accelerating its conversion to inactive GDPRas. In schwannoma cell lines from patients with neuroffbromatosis, loss of neurofibromin was previously shown to be associated with impaired regulation of GTP Ras. Our analysis of other neural crest-derived tumor cell lines has shown that some melanoma and neuroblastoma cell lines established from tumors occurring in patients without neurofibromatosis contain reduced or undetectable levels of neurofibromin, with concomitant genetic abnormalities of the NFI locus. In contrast to the schwannoma cell lines, GTP Ras was appropriately regulated in the melanoma and neuroblastoma lines that were deficient in neuroflbromin, even when c-H-ras was overexpressed in the lines. These results demonstrate that some neural crest tumors not associated with neurofibromatosis have acquired somatically inactivated NFI genes and suggest a tumor-suppressor function for neurofibromin that is independent of Ras GTPase activation.