Bipartite interaction between neurofibromatosis type I protein (neurofibromin) and syndecan transmembrane heparan sulfate proteoglycans.
The neurofibromatosis type 1 (NF1) gene encodes a large tumor suppressor protein (neurofibromin). Although it is known to possess Ras GTPase-activating protein (GAP) activity, the cellular role of neurofibromin remains unclear. Here we used yeast two-hybrid screening to identify neurofibromin-interacting proteins. Syndecan-2, a transmembrane heparan sulfate proteoglycan (HSPG), was isolated as a binding partner for two distinct regions of the neurofibromin protein. We subsequently found that neurofibromin can bind all four mammalian syndecans. NF1 interaction requires the transmembrane domain and a membrane-proximal region of the cytoplasmic tail of syndecan, but not the C terminus of syndecan known to bind to CASK, a membrane-associated guanylate kinase (MAGUK). Neurofibromin, syndecans, and CASK have overlapping subcellular distributions in axons and synapses of neurons, as shown by biochemical fractionation and immunostaining. Moreover, neurofibromin exists in a complex with syndecan and CASK in vivo, as evidenced by their coimmunoprecipitation from rat brain. Our findings suggest that interaction with different members of the syndecan family may be a mechanism for localizing neurofibromin to specialized domains of the plasma membrane.
Hsueh
Y P
YP
Institute of Molecular Biology, Academia Sinica, Taipei, Taiwan, 115, Republic of China. yph@gate.sinica.edu.tw
Roberts
A M
AM
Volta
M
M
Sheng
M
M
Roberts
R G
RG
D000818:Animals; D001921:Brain / Q000378:metabolism; D001923:Brain Chemistry; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D051528:Guanylate Kinases; D019812:Heparan Sulfate Proteoglycans / Q000378:metabolism*; D006801:Humans; D046911:Macromolecular Substances; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism*; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism*; D009456:Neurofibromatosis 1 / Q000235:genetics; D025542:Neurofibromin 1; D009703:Nucleoside-Phosphate Kinase / Q000378:metabolism; D011233:Precipitin Tests; D011485:Protein Binding / Q000502:physiology; D017434:Protein Structure, Tertiary / Q000502:physiology; D011509:Proteoglycans / Q000235:genetics / Q000378:metabolism*; D051381:Rats; D012440:Saccharomyces / Q000235:genetics; D013347:Subcellular Fractions / Q000737:chemistry / Q000378:metabolism; D053669:Syndecan-2; D053670:Syndecan-3; D053667:Syndecans; D020798:Two-Hybrid System Techniques
D019812:Heparan Sulfate Proteoglycans; D046911:Macromolecular Substances; D008562:Membrane Glycoproteins; D009419:Nerve Tissue Proteins; D025542:Neurofibromin 1; D011509:Proteoglycans; C508245:SDC2 protein, human; C508301:SDC3 protein, human; C508247:Sdc2 protein, rat; C508303:Sdc3 protein, rat; D053670:Syndecan-3; D053667:Syndecans; D053669:Syndecan-2; C106868:CASK kinases; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D009703:Nucleoside-Phosphate Kinase; D051528:Guanylate Kinases