title: Farnesylthiosalicylic acid (salirasib) inhibits Rheb in TSC2-null ELT3 cells: a potential treatment for lymphangioleiomyomatosis.
abstract: The small GTPase proteins, Ras and Rheb, serve as molecular switches regulating cell proliferation, differentiation and apoptosis. Ras also regulates Rheb by inactivating the tuberous sclerosis complex (TSC), which includes products of the TSC1 and TSC2 genes encoding hamartin (TSC1) and tuberin (TSC2), respectively, and acts as a Rheb-specific GTPase-activating protein. Loss of function of TSC1 or TSC2 results in an increase in active Rheb.GTP with the consequent translational abnormalities and excessive cell proliferation characteristic of the genetic disorders, tuberous sclerosis and lymphangioleiomyomatosis (LAM). To determine whether inactivation of Rheb, Ras or both might be a potential treatment for LAM, we used TSC2-null ELT3 cells as a LAM model. The cells were treated with the Ras inhibitor S-trans,trans-farnesylthiosalicylic acid (FTS; salirasib), which mimics the C-terminal S-farnesyl cysteine common to Ras and Rheb. This C-terminus is critical for their attachment to cellular membranes and for their biological activities. Untreated, the ELT3 cells expressed significant amounts of Rheb but little Ras.GTP, and this phenotype was reversed by TSC2 reexpression. Treatment with FTS decreased Ras.GTP only slightly in the TSC2-null cells, but reduced their overactive Rheb as well as their proliferation, migration and tumor growth. Notably, TSC2 reexpression in these ELT3 cells rescued them from the inhibitory effect of FTS. Evidently, therefore, FTS blocks active Rheb in TSC2-null ELT3 cells and may have therapeutic potential for LAM.
authors.affiliation: Department of Neurobiology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel.
authors.forename: Victoria
authors.initials: V
authors.lastname: Makovski
authors.forename: Roni
authors.initials: R
authors.lastname: Haklai
authors.forename: Yoel
authors.initials: Y
authors.lastname: Kloog
mesh_terms: D000818:Animals; D045744:Cell Line, Tumor; D002465:Cell Movement / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D003545:Cysteine / Q000031:analogs & derivatives / Q000378:metabolism; D005204:Farnesol / Q000031:analogs & derivatives* / Q000494:pharmacology; D018192:Lymphangioleiomyomatosis / Q000188:drug therapy* / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D008215:Lymphocytes, Null; D051379:Mice; D008819:Mice, Nude; D020559:Monomeric GTP-Binding Proteins / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D009154:Mutation / Q000235:genetics; D009479:Neuropeptides / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D000076205:Ras Homolog Enriched in Brain Protein; D051381:Rats; D019893:Ribosomal Protein S6 Kinases / Q000378:metabolism; D012459:Salicylates / Q000494:pharmacology*; D000077005:Tuberous Sclerosis Complex 2 Protein; D025521:Tumor Suppressor Proteins / Q000172:deficiency* / Q000235:genetics / Q000378:metabolism; D018631:ras Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D009479:Neuropeptides; D000076205:Ras Homolog Enriched in Brain Protein; C087693:Rheb protein, rat; D012459:Salicylates; C000624654:Tsc2 protein, mouse; C000624655:Tsc2 protein, rat; D000077005:Tuberous Sclerosis Complex 2 Protein; D025521:Tumor Suppressor Proteins; C093323:farnesylthiosalicylic acid; D005204:Farnesol; C057785:S-farnesylcysteine; D019893:Ribosomal Protein S6 Kinases; D020559:Monomeric GTP-Binding Proteins; D018631:ras Proteins; D003545:Cysteine