PMCC PMCC

Search tips
Search criteria

Advanced
Results 1-9 (9)
 

Clipboard (0)
None

Select a Filter Below

Journals
Year of Publication
1.  The cyclin-dependent kinase PITSLRE/CDK11 is required for successful autophagy 
Autophagy  2011;7(11):1295-1301.
(Macro)autophagy is a membrane-trafficking process that serves to sequester cellular constituents in organelles termed autophagosomes, which target their degradation in the lysosome. Autophagy operates at basal levels in all cells where it serves as a homeostatic mechanism to maintain cellular integrity. The levels and cargoes of autophagy can, however, change in response to a variety of stimuli, and perturbations in autophagy are known to be involved in the etiology of various human diseases. Autophagy must therefore be tightly controlled. We report here that the Drosophila cyclindependent kinase PITSLRE is a modulator of autophagy. Loss of the human PITSLRE ortholog, CDK11, initially appears to induce autophagy, but at later time points CDK11 is critically required for autophagic flux and cargo digestion. Since PITSLRE/CDK11 regulates autophagy in both Drosophila and human cells, this kinase represents a novel phylogenetically conserved component of the autophagy machinery.
doi:10.4161/auto.7.11.16646
PMCID: PMC3242795  PMID: 21808150
PITSLRE; CDK11; cyclin-dependent kinase; autophagy; human; Drosophila
2.  Actomyosin-mediated cellular tension drives increased tissue stiffness and β-catenin activation to induce interfollicular epidermal hyperplasia and tumor growth 
Cancer cell  2011;19(6):776-791.
SUMMARY
Tumors and associated stroma manifest mechanical properties that promote cancer. Mechanosensation of tissue stiffness activates the Rho/ROCK pathway to increase actomyosin-mediated cellular tension to re-establish force equilibrium. To determine how actomyosin tension affects tissue homeostasis and tumor development, we expressed conditionally-active ROCK2 in mouse skin. ROCK activation elevated tissue stiffness via increased collagen. β-catenin, a key element of mechanotranscription pathways, was stabilized by ROCK activation leading to nuclear accumulation, transcriptional activation and consequent hyperproliferation and skin thickening. Inhibiting actomyosin contractility by blocking LIMK or myosin ATPase attenuated these responses, as did FAK inhibition. Tumor number, growth and progression were increased by ROCK activation, while ROCK blockade was inhibitory, implicating actomyosin-mediated cellular tension and consequent collagen deposition as significant tumor promoters.
doi:10.1016/j.ccr.2011.05.008
PMCID: PMC3115541  PMID: 21665151
3.  p53-mediated transcriptional regulation and activation of the actin cytoskeleton regulatory RhoC to LIMK2 signaling pathway promotes cell survival 
Cell Research  2010;21(4):666-682.
The central arbiter of cell fate in response to DNA damage is p53, which regulates the expression of genes involved in cell cycle arrest, survival and apoptosis. Although many responses initiated by DNA damage have been characterized, the role of actin cytoskeleton regulators is largely unknown. We now show that RhoC and LIM kinase 2 (LIMK2) are direct p53 target genes induced by genotoxic agents. Although RhoC and LIMK2 have well-established roles in actin cytoskeleton regulation, our results indicate that activation of LIMK2 also has a pro-survival function following DNA damage. LIMK inhibition by siRNA-mediated knockdown or selective pharmacological blockade sensitized cells to radio- or chemotherapy, such that treatments that were sub-lethal when administered singly resulted in cell death when combined with LIMK inhibition. Our findings suggest that combining LIMK inhibitors with genotoxic therapies could be more efficacious than single-agent administration, and highlight a novel connection between actin cytoskeleton regulators and DNA damage-induced cell survival mechanisms.
doi:10.1038/cr.2010.154
PMCID: PMC3145139  PMID: 21079653
LIMK; RhoC; p53; DNA damage; actin; cofilin; cytoskeleton
4.  p53-mediated transcription and activation of the actin cytoskeleton regulatory RhoC to LIMK2 signaling pathway promotes cell survival 
Cell research  2010;21(4):666-682.
The central arbiter of cell fate in response to DNA damage is p53, which regulates the expression of genes involved in cell cycle arrest, survival and apoptosis. Although many responses initiated by DNA damage have been characterized, the role of actin cytoskeleton regulators is largely unknown. We now show that RhoC and LIMK2 are direct p53 target genes induced by genotoxic agents. Although RhoC and LIMK2 have well-established roles in actin cytoskeleton regulation, our results indicate that activation of LIMK2 also has a pro-survival function following DNA damage. LIMK inhibition by siRNA-mediated knockdown or selective pharmacological blockade sensitized cells to radio- or chemotherapy, such that treatments which were sub-lethal when administered singly resulted in cell death when combined with LIMK inhibition. Our findings suggest that combining LIMK inhibitors with genotoxic therapies could be more efficacious than single-agent administration, and highlight a novel connection between actin cytoskeleton regulators and DNA damage-induced cell survival mechanisms.
doi:10.1038/cr.2010.154
PMCID: PMC3145139  PMID: 21079653
LIMK; RhoC; p53; DNA damage; actin; cofilin; cytoskeleton
5.  Transcriptional regulation of Rho GTPase signaling 
Transcription  2011;2(5):211-215.
Signaling through the Rho family of small GTPases regulates a variety of cellular processes via changes in the actin cytoskeleton. Here we discuss recent findings that show the transcription factor p53 regulates the expression of several Rho pathway signaling molecules, and how mutation of p53 in cancer dramatically alters signaling output through this pathway.
doi:10.4161/trns.2.5.16904
PMCID: PMC3265777  PMID: 22231116
Rho GTPases; RhoA; RhoB; RhoC; RhoE; LIMK; p53; miRNA; DNA damage; actin; cofilin; cytoskeleton
6.  LIM kinases are required for invasive path generation by tumor and tumor-associated stromal cells 
The Journal of Cell Biology  2010;191(1):169-185.
Leading cells require LIMK for matrix degradation and invadopodia formation during collective cell migration.
LIM kinases 1 and 2 (LIMK1/2) are centrally positioned regulators of actin cytoskeleton dynamics. Using siRNA-mediated knockdown or a novel small molecule inhibitor, we show LIMK is required for path generation by leading tumor cells and nontumor stromal cells during collective tumor cell invasion. LIMK inhibition lowers cofilin phosphorylation, F-actin levels, serum response factor transcriptional activity and collagen contraction, and reduces invasion in three-dimensional invasion assays. Although motility was unaffected, LIMK inhibition impairs matrix protein degradation and invadopodia formation associated with significantly faster recovery times in FRAP assays indicative of reduced F-actin stability. When LIMK is knocked down in MDA-MB-231 cells, they lose the ability to lead strands of collectively invading cells. Similarly, when LIMK activity is blocked in cancer-associated fibroblasts, they are unable to lead the collective invasion of squamous carcinoma cells in an organotypic skin model. These results show that LIMK is required for matrix remodeling activities for path generation by leading cells in collective invasion.
doi:10.1083/jcb.201002041
PMCID: PMC2953444  PMID: 20876278
7.  The Rho GTPase Effector ROCK Regulates Cyclin A, Cyclin D1, and p27Kip1 Levels by Distinct Mechanisms 
Molecular and Cellular Biology  2006;26(12):4612-4627.
The members of the Rho GTPase family are well known for their regulation of actin cytoskeletal structures. In addition, they influence progression through the cell cycle. The RhoA and RhoC proteins regulate numerous effector proteins, with a central and vital signaling role mediated by the ROCK I and ROCK II serine/threonine kinases. The requirement for ROCK function in the proliferation of numerous cell types has been revealed by studies utilizing ROCK-selective inhibitors such as Y-27632. However, the mechanisms by which ROCK signaling promotes cell cycle progression have not been thoroughly characterized. Using a conditionally activated ROCK-estrogen receptor fusion protein, we found that ROCK activation is sufficient to stimulate G1/S cell cycle progression in NIH 3T3 mouse fibroblasts. Further analysis revealed that ROCK acts via independent pathways to alter the levels of cell cycle regulatory proteins: cyclin D1 and p21Cip1 elevation via Ras and the mitogen-activated protein kinase pathway, increased cyclin A via LIM kinase 2, and reduction of p27Kip1 protein levels. Therefore, the influence of ROCK on cell cycle regulatory proteins occurs by multiple independent mechanisms.
doi:10.1128/MCB.02061-05
PMCID: PMC1489131  PMID: 16738326
8.  AP-1 Differentially Expressed Proteins Krp1 and Fibronectin Cooperatively Enhance Rho-ROCK-Independent Mesenchymal Invasion by Altering the Function, Localization, and Activity of Nondifferentially Expressed Proteins†  
Molecular and Cellular Biology  2006;26(4):1480-1495.
The transcription factor AP-1, which is composed of Fos and Jun family proteins, plays an essential role in tumor cell invasion by altering gene expression. We report here that Krp1, the AP-1 up-regulated protein that has a role in pseudopodial elongation in v-Fos-transformed rat fibroblast cells, forms a novel interaction with the nondifferentially expressed actin binding protein Lasp-1. Krp1 and Lasp-1 colocalize with actin at the tips of pseudopodia, and this localization is maintained by continued AP-1 mediated down-regulation of fibronectin that in turn suppresses integrin and Rho-ROCK signaling and allows pseudopodial protrusion and mesenchyme-like invasion. Mutation analysis of Lasp-1 demonstrates that its SH3 domain is necessary for pseudopodial extension and invasion. The results support the concept of an AP-1-regulated multigenic invasion program in which proteins encoded by differentially expressed genes direct the function, localization, and activity of proteins that are not differentially expressed to enhance the invasiveness of cells.
doi:10.1128/MCB.26.4.1480-1495.2006
PMCID: PMC1367185  PMID: 16449658
9.  Actin-myosin–based contraction is responsible for apoptotic nuclear disintegration 
The Journal of Cell Biology  2005;168(2):245-255.
Membrane blebbing during the apoptotic execution phase results from caspase-mediated cleavage and activation of ROCK I. Here, we show that ROCK activity, myosin light chain (MLC) phosphorylation, MLC ATPase activity, and an intact actin cytoskeleton, but not microtubular cytoskeleton, are required for disruption of nuclear integrity during apoptosis. Inhibition of ROCK or MLC ATPase activity, which protect apoptotic nuclear integrity, does not affect caspase-mediated degradation of nuclear proteins such as lamins A, B1, or C. The conditional activation of ROCK I was sufficient to tear apart nuclei in lamin A/C null fibroblasts, but not in wild-type fibroblasts. Thus, apoptotic nuclear disintegration requires actin-myosin contractile force and lamin proteolysis, making apoptosis analogous to, but distinct from, mitosis where nuclear disintegration results from microtubule-based forces and from lamin phosphorylation and depolymerization.
doi:10.1083/jcb.200409049
PMCID: PMC2171584  PMID: 15657395

Results 1-9 (9)