LIM domain kinases as potential therapeutic targets for neurofibromatosis type 2.
Neurofibromatosis type 2 (NF2) is caused by mutations in the NF2 gene that encodes a tumor-suppressor protein called merlin. NF2 is characterized by formation of multiple schwannomas, meningiomas and ependymomas. Merlin loss-of-function is associated with increased activity of Rac and p21-activated kinases (PAKs) and deregulation of cytoskeletal organization. LIM domain kinases (LIMK1 and 2) are substrate for Cdc42/Rac-PAK and modulate actin dynamics by phosphorylating cofilin at serine-3. This modification inactivates the actin severing and depolymerizing activity of cofilin. LIMKs also translocate into the nucleus and regulate cell cycle progression. Significantly, LIMKs are overexpressed in several tumor types, including skin, breast, lung, liver and prostate. Here we report that mouse Schwann cells (MSCs) in which merlin function is lost as a result of Nf2 exon2 deletion (Nf2(ΔEx2)) exhibited increased levels of LIMK1, LIMK2 and active phospho-Thr508/505-LIMK1/2, as well as phospho-Ser3-cofilin, compared with wild-type normal MSCs. Similarly, levels of LIMK1 and 2 total protein and active phosphorylated forms were elevated in human vestibular schwannomas compared with normal human Schwann cells (SCs). Reintroduction of wild-type NF2 into Nf2(ΔEx2) MSC reduced LIMK1 and LIMK2 levels. We show that pharmacological inhibition of LIMK with BMS-5 decreased the viability of Nf2(ΔEx2) MSCs in a dose-dependent manner, but did not affect viability of control MSCs. Similarly, LIMK knockdown decreased viability of Nf2(ΔEx2) MSCs. The decreased viability of Nf2(ΔEx2) MSCs was not due to caspase-dependent or -independent apoptosis, but rather due to inhibition of cell cycle progression as evidenced by accumulation of cells in G2/M phase. Inhibition of LIMKs arrests cells in early mitosis by decreasing aurora A activation. Our results suggest that LIMKs are potential drug targets for NF2 and tumors associated with merlin deficiency.
Department of Biomedical Science, College of Medicine, University of Central Florida, Orlando, FL, USA.
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Petrilli
Department of Biomedical Science, College of Medicine, University of Central Florida, Orlando, FL, USA.
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Copik
Department of Biomedical Science, College of Medicine, University of Central Florida, Orlando, FL, USA.
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Posadas
1] Center for Childhood Cancer, Research Institute at Nationwide Children's Hospital, Columbus, OH, USA [2] Department of Pediatrics, Ohio State University College of Medicine, Columbus, OH, USA.
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Chang
Department of Otolaryngology, Ohio State University College of Medicine, Columbus, OH, USA.
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Welling
Division of Clinical and Translational Research, House Research Institute, Los Angeles, CA, USA.
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Giovannini
Department of Biomedical Science, College of Medicine, University of Central Florida, Orlando, FL, USA.
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Fernández-Valle
D051339:Actin Depolymerizing Factors / Q000378:metabolism; D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D064096:Aurora Kinase A / Q000378:metabolism; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D059565:G2 Phase Cell Cycle Checkpoints / Q000187:drug effects; D020868:Gene Silencing; D006801:Humans; D054461:Lim Kinases / Q000037:antagonists & inhibitors / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D059566:M Phase Cell Cycle Checkpoints / Q000187:drug effects; D051379:Mice; D008938:Mitosis / Q000187:drug effects; D058990:Molecular Targeted Therapy; D016518:Neurofibromatosis 2 / Q000188:drug therapy* / Q000201:enzymology* / Q000378:metabolism / Q000473:pathology; D025581:Neurofibromin 2 / Q000235:genetics / Q000378:metabolism; D010750:Phosphoproteins / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D047428:Protein Kinase Inhibitors / Q000494:pharmacology* / Q000627:therapeutic use; D012583:Schwann Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism / Q000473:pathology
D051339:Actin Depolymerizing Factors; D025581:Neurofibromin 2; D010750:Phosphoproteins; D047428:Protein Kinase Inhibitors; D064096:Aurora Kinase A; D054461:Lim Kinases