6wgh | pdb_00006wgh
Crystal structure of GDP-bound NRAS with ten residues long internal tandem duplication in the switch II region
Structural highlights
Disease[RASN_HUMAN] Defects in NRAS are a cause of juvenile myelomonocytic leukemia (JMML) [MIM:607785]. JMML is a pediatric myelodysplastic syndrome that constitutes approximately 30% of childhood cases of myelodysplastic syndrome (MDS) and 2% of leukemia. Defects in NRAS are the cause of Noonan syndrome type 6 (NS6) [MIM:613224]. A syndrome characterized by facial dysmorphic features such as hypertelorism, a downward eyeslant and low-set posteriorly rotated ears. Other features can include short stature, a short neck with webbing or redundancy of skin, cardiac anomalies, deafness, motor delay and variable intellectual deficits.[1] Defects in NRAS are the cause of autoimmune lymphoproliferative syndrome type 4 (ALPS4) [MIM:614470]. A disorder of apoptosis, characterized by chronic accumulation of non-malignant lymphocytes, defective lymphocyte apoptosis, and an increased risk for the development of hematologic malignancies.[2] Function[RASN_HUMAN] Ras proteins bind GDP/GTP and possess intrinsic GTPase activity. Publication Abstract from PubMedThe oncogene RAS is one of the most widely studied proteins in cancer biology, and mutant-active RAS is a driver in many types of solid tumors and hematological malignancies. Yet the biological effects of different RAS mutations and the tissue-specific clinical implications are complex and nuanced. Here, we identified an internal tandem duplication (ITD) in the switch II domain of NRAS from a patient with extremely aggressive colorectal carcinoma. Results of whole-exome DNA sequencing of primary and metastatic tumors indicated that this mutation was present in all analyzed metastases and excluded the presence of any other clear oncogenic driver mutations. Biochemical analysis revealed increased interaction of the RAS ITD with Raf proto-oncogene Ser/Thr kinase (RAF), leading to increased phosphorylation of downstream MAPK/ERK kinase (MEK)/extracellular signal-regulated kinase (ERK). The ITD prevented interaction with neurofibromin 1 (NF1)-GTPase-activating protein (GAP), providing a mechanism for sustained activity of the RAS ITD protein. We present the first crystal structures of NRAS and KRAS ITD at 1.65-1.75 A resolutions, respectively, providing insight into the physical interactions of this unique class of RAS variants with its regulatory and effector proteins. Our in-depth bedside-to-bench analysis uncovers the molecular mechanism underlying a case of highly aggressive colorectal cancer and illustrates the importance of robust biochemical and biophysical approaches in the implementation of individualized medicine. RAS internal tandem duplication disrupts GTPase-activating protein (GAP) binding to activate oncogenic signaling.,Nelson AC, Turbyville TJ, Dharmaiah S, Rigby M, Yang R, Wang TY, Columbus J, Stephens R, Taylor T, Sciacca D, Onsongo G, Sarver A, Subramanian S, Nissley DV, Simanshu DK, Lou E J Biol Chem. 2020 May 11. pii: RA119.011080. doi: 10.1074/jbc.RA119.011080. PMID:32393580[3] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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