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1.  Targeting the KIT Activating Switch Control Pocket: A Novel Mechanism to Inhibit Neoplastic Mast Cell Proliferation and Mast Cell Activation 
Activating mutations in the receptor tyrosine kinase KIT, most notably KIT D816V, are commonly observed in patients with systemic mastocytosis. Thus, inhibition of KIT has been a major focus for treatment of this disorder. Here we investigated a novel approach to such inhibition. Utilizing rational drug design, we targeted the switch pocket (SP) of KIT which regulates its catalytic conformation. Two SP inhibitors thus identified, DP-2976 and DP-4851, were examined for effects on neoplastic mast cell proliferation and mast cell activation. Autophosphorylation of both wild type (WT) and, where also examined, KIT D816V was blocked by these compounds in transfected 293T cells, HMC 1.1 and 1.2 human mast cell lines; and in CD34+-derived human mast cells activated by stem cell factor (SCF). Both inhibitors induced apoptosis in the neoplastic mast cell lines and reduced survival of primary bone marrow mast cells from patients with mastocytosis. Moreover, the SP inhibitors more selectively blocked SCF potentiation of FcεRI-mediated degranulation. Overall, SP inhibitors represent an innovative mechanism of KIT inhibition whose dual suppression of KIT D816V neoplastic mast cell proliferation and SCF enhanced mast cell activation may provide significant therapeutic benefits.
doi:10.1038/leu.2012.218
PMCID: PMC3529859  PMID: 22907049
mastocytosis; switch pocket; KIT; KIT D816V; tyrosine kinase inhibitor; mast cell
2.  Translation validation of a new back pain screening questionnaire (the STarT Back Screening Tool) in French 
Archives of Public Health  2012;70(1):12.
Background
Low back pain (LBP) is a major public health problem and the identification of individuals at risk of persistent LBP poses substantial challenges to clinical management. The STarT Back questionnaire is a validated nine-item patient self-report questionnaire that classifies patients with LBP at low, medium or high-risk of poor prognosis for persistent non-specific LBP. The objective of this study was to translate and cross-culturally adapt the English version of the STarT Back questionnaire into French.
Methods
The translation was performed using best practice translation guidelines. The following phases were performed: contact with the STarT Back questionnaire developers, initial translations (English into French), synthesis, back translations, expert committee review, test of the pre-final version on 44 individuals with LBP, final version.
Results
The linguistic translation required minor semantic alterations. The participants interviewed indicated that all items of the questionnaire were globally clear and comprehensible. However, 6 subjects (14%) wondered if two questions were related to back pain or general health. After discussion within the expert committee and with the developer of the STarT Back tool, it was decided to modify the questionnaire and to add a reference to back pain in these two questions.
Conclusions
The French version of the STarT Back questionnaire has been shown to be comprehensible and adapted to the French speaking general population. Investigations are now required to test the psychometric properties (reliability, internal and external validity, responsiveness) of this translated version of the questionnaire.
doi:10.1186/0778-7367-70-12
PMCID: PMC3436683  PMID: 22958224
Low back pain; Questionnaire; Translation
3.  AFAP1L1 is a novel adaptor protein of the AFAP family that interacts with cortactin and localizes to invadosomes 
European journal of cell biology  2011;90(5):376-389.
The actin-filament associated protein (AFAP) family of adaptor proteins consists of three members: AFAP1, AFAP1L1, and AFAP1L2/XB130 with AFAP1 being the best described as a cSrc binding partner and actin cross-linking protein. A homology search of AFAP1 recently identified AFAP1L1 which has a similar sequence, domain structure and cellular localization; however, based upon sequence variations, AFAP1L1 is hypothesized to have unique functions that are distinct from AFAP1. While AFAP1 has the ability to bind to the SH3 domain of the nonreceptor tyrosine kinase cSrc via an N-terminal SH3 binding motif, it was unable to bind cortactin. However, the SH3 binding motif of AFAP1L1 was more efficient at interacting with the SH3 domain of cortactin and not cSrc. AFAP1L1 was shown by fluorescence microscopy to decorate actin filaments and move to punctate actin structures and colocalize with cortactin, consistent with localization to invadosomes. Upon overexpression in A7r5 cells, AFAP1L1 had the ability to induce podosome formation and move to podosomes without stimulation. Immunohistochemical analysis of AFAP1L1 in human tissues shows differential expression when contrasted with AFAP1 with localization of AFAP1L1 to unique sites in muscle and the dentate nucleus of the brain where AFAP1 was not detectable. We hypothesize AFAP1L1 may play a similar role to AFAP1 in affecting changes in actin filaments and bridging interactions with binding partners, but we hypothesize that AFAP1L1 may forge unique protein interactions in which AFAP1 is less efficient, and these interactions may allow AFAP1L1 to affect invadosome formation.
doi:10.1016/j.ejcb.2010.11.016
PMCID: PMC3085893  PMID: 21333378
AFAP1L1; AFAP1; XB130; podosome; cortactin; dentate nucleus; actin
4.  Conformational control inhibition of the BCR-ABL1 tyrosine kinase, including the gatekeeper T315I mutant, by the switch-control inhibitor DCC-2036 
Cancer cell  2011;19(4):556-568.
Summary
Acquired resistance to ABL1 tyrosine kinase inhibitors (TKIs) through ABL1 kinase domain mutations, particularly the gatekeeper mutant T315I, is a significant problem for chronic myeloid leukemia (CML) patients. Using structure-based drug design, we developed compounds that bind to residues (Arg386/Glu282) ABL1 uses to switch between inactive and active conformations. The lead “switch-control” inhibitor, DCC-2036, potently inhibits both unphosphorylated and phosphorylated ABL1 by inducing a type II inactive conformation, and retains efficacy against the majority of clinically relevant CML resistance mutants, including T315I. DCC-2036 inhibits BCR-ABL1T315I-expressing cell lines, prolongs survival in mouse models of T315I-mutant CML and B-lymphoblastic leukemia, and inhibits primary patient leukemia cells expressing T315I in vitro and in vivo, supporting its clinical development in TKI-resistant Ph+ leukemia.
doi:10.1016/j.ccr.2011.03.003
PMCID: PMC3077923  PMID: 21481795
5.  Monomer-on-Monomer (MoM) Mitsunobu Reaction: Facile Purification Utilizing Surface-Initiated Sequestration 
Organic Letters  2010;13(1):8-10.
A monomer-on-monomer (MoM) Mitsunobu reaction utilizing norbornenyl-tagged (Nb-tagged) reagents is reported, whereby purification was rapidly achieved by employing ring-opening metathesis polymerization which is initiated by any of three methods utilizing Grubbs catalyst (i) free catalyst in solution, (ii) surface-initiated catalyst-armed silica or (iii) surface-initiated catalyst-armed Co/C magnetic nanoparticles.
doi:10.1021/ol1022382
PMCID: PMC3271942  PMID: 21121636
6.  High-load, oligomeric dichlorotriazine (ODCT): A versatile ROMP-derived reagent and scavenger 
The Journal of Organic Chemistry  2008;73(22):8785-8790.
A new high-load, soluble oligomeric dichlorotriazine (ODCT) reagent derived from ring-opening metathesis polymerization (ROMP) is reported as an effective coupling reagent, scavenger of nucleophilic species and activator of DMSO for the classic Swern oxidations. Two variants of this reagent 2GODCT 4 and 1GODCT 16, possessing theoretical loads of 5.3 mmol/g and 7.3 mmol/g, respectively, have been synthesized. Preparation was accomplished via simple synthetic protocols affording free flowing powders, amenable for large-scale production. Removal of the spent oligomeric reagent was achieved via either precipitation of the spent reagent or simple filtration utilizing a silica SPE, followed by solvent removal, to deliver products in excellent yield and purity. In addition, the corresponding norbornenyl monomer 3 was successfully demonstrated in a couple-ROMP-filter protocol utilizing in-situ polymerization, achieving comparable results versus the corresponding oligomeric variant.
doi:10.1021/jo801578f
PMCID: PMC3271944  PMID: 18937412
Ring-Opening Metathesis Polymerization (ROMP); Dichlorotriazine (DCT); Trichlorotriazine (TCT); Oligomer; High-Load; Scavenger; Coupling Reagent; Swern Oxidation
7.  The ABL switch control inhibitor DCC-2036 is active against the chronic myeloid leukemia mutant BCR-ABLT315I and exhibits a narrow resistance profile 
Cancer research  2011;71(9):3189-3195.
Acquired point mutations within the BCR-ABL kinase domain represent a common mechanism of resistance to ABL inhibitor therapy in patients with chronic myeloid leukemia (CML). The BCR-ABLT315I mutant is highly resistant to imatinib, nilotinib, and dasatinib and is frequently detected in relapsed patients. This critical gap in resistance coverage drove development of DCC-2036, an ABL inhibitor which binds the switch control pocket involved in conformational regulation of the kinase domain. We evaluated the efficacy of DCC-2036 against BCR-ABLT315I and other mutants in cellular and biochemical assays and conducted cell-based mutagenesis screens. DCC-2036 inhibited autophosphorylation of ABL and ABLT315I enzymes, and this activity was consistent with selective efficacy against Ba/F3 cells expressing BCR-ABL (IC50: 19 nmol/L), BCR-ABLT315I (IC50: 63 nmol/L), and most kinase domain mutants. Ex vivo exposure of CML cells from patients harboring BCR-ABL or BCR-ABLT315I to DCC-2036 revealed marked inhibition of colony formation and reduced phosphorylation of the direct BCR-ABL target CrkL. Cell-based mutagenesis screens identified a resistance profile for DCC-2036 centered around select P-loop mutations (G250E, Q252H, Y253H, E255K/V), although a concentration of 750 nmol/L DCC-2036 suppressed the emergence of all resistant clones. A decreased concentration of DCC-2036 (160 nmol/L) in dual-combination with either nilotinib or dasatinib achieved the same zero outgrowth result. Further screens for resistance due to BCR-ABL compound mutations (two mutations in the same clone) identified BCR-ABLE255V / T315I as the most resistant mutant. Taken together, these findings support continued evaluation of DCC-2036 as an important new agent for treatment-refractory CML.
doi:10.1158/0008-5472.CAN-10-3224
PMCID: PMC3206627  PMID: 21505103
BCR-ABL; imatinib resistance; DCC-2036
8.  Targeted Inhibition of Multiple Receptor Tyrosine Kinases in Mesothelioma12 
Neoplasia (New York, N.Y.)  2011;13(1):12-22.
The receptor tyrosine kinases (RTKs) epidermal growth factor receptor (EGFR) and MET are activated in subsets of mesothelioma, suggesting that these kinases might represent novel therapeutic targets in this notoriously chemotherapy-resistant cancer. However, clinical trials have shown little activity for EGFR inhibitors in mesothelioma. Despite the evidence for RTK activation in mesothelioma pathogenesis, it is unclear whether transforming activity is dependent on an individual kinase oncoprotein or the coordinated activity of multiple kinases. Using phospho-RTK and immunoblot assays, we herein demonstrate activation of multiple RTKs (EGFR, MET, AXL, and ERBB3) in individual mesothelioma cell lines but not in normal mesothelioma cells. Inhibition of mesothelioma multi-RTK signaling was accomplished using combinations of RTK direct inhibitors or by inhibition of the RTK chaperone, heat shock protein 90 (HSP90). Multi-RTK inhibition by the HSP90 inhibitor 17-allyloamino-17-demethoxygeldanamycin (17-AAG) had a substantially greater effect on mesothelioma proliferation and survival compared with inhibition of individual activated RTKs. HSP90 inhibition also suppressed phosphorylation of downstream signaling intermediates (AKT, mitogen-activated protein kinase, and S6); upregulated the p53, p21, and p27 cell cycle checkpoints; induced G2 phase arrest; induced caspase 3/7 activity; and led to an increase in the sub-G1 apoptotic population. These compelling proapoptotic and antiproliferative responses indicate that HSP90 inhibition warrants clinical evaluation as a novel therapeutic strategy in mesothelioma.
PMCID: PMC3022424  PMID: 21245936
9.  A Polymorphic Variant of AFAP-110 Enhances cSrc Activity12 
Translational Oncology  2010;3(4):276-285.
Enhanced expression and activity of cSrc are associated with ovarian cancer progression. Generally, cSrc does not contain activating mutations; rather, its activity is increased in response to signals that affect a conformational change that releases its autoinhibition. In this report, we analyzed ovarian cancer tissues for the expression of a cSrc-activating protein, AFAP-110. AFAP-110 activates cSrc through a direct interaction that releases it from its autoinhibited conformation. Immunohistochemical analysis revealed a concomitant increase of AFAP-110 and cSrc in ovarian cancer tissues. An analysis of the AFAP-110 coding sequence revealed the presence of a nonsynonymous, single-nucleotide polymorphism that resulted in a change of Ser403 to Cys403. In cells that express enhanced levels of cSrc, AFAP-110403C directed the activation of cSrc and the formation of podosomes independently of input signals, in contrast to wild-type AFAP-110. We therefore propose that, under conditions of cSrc overexpression, the polymorphic variant of AFAP-110 promotes cSrc activation. Further, these data indicate amechanismby which an inherited genetic variation could influence ovarian cancer progression and could be used to predict the response to targeted therapy.
PMCID: PMC2915419  PMID: 20689769
10.  Confirmation of gene expression-based prediction of survival in non-small cell lung cancer 
Clinical Relevance
It remains a critical issue to reliably identify specific patients at high risk for recurrence and metastasis of lung cancer. To date, there has been no clinically applied gene test for predicting lung cancer recurrence. This study validated a 35-gene prognostic signature in various cell types of non-small cell lung cancer. The analysis showed that the 35-gene signature could further stratify patients at stage 1A into distinct prognostic subgroups. This lung cancer prognostic signature is independent of traditional clinicopathological factors, including patient age, clinical stage, tumor differentiation, and tumor grade. This signature had better prognostic performance than other lung cancer signatures, including the 5-gene signature and the 133-gene signature in the studied cohorts. The gene expression and protein expression of the identified biomarkers were validated in real-time RT-PCR and Western blots analysis of clinical specimens. This study indicates that the 35-gene signature could be applied in clinics for patient stratification.
Purpose
It remains a critical challenge to determine the risk for recurrence in early stage non-small cell lung cancer (NSCLC) patients. Accurate gene expression signatures are needed to classify patients into high- and low-risk groups to improve the selection of patients for adjuvant therapy.
Experimental Design
Multiple published microarray datasets were used to evaluate our previously identified lung cancer prognostic gene signature. Expression of the signature genes was further validated with real-time RT-PCR and Western blot assays of snap frozen lung cancer tumor tissues.
Results
Our previously identified 35-gene signature stratified 264 patients with non-small cell lung cancer into high- and low-risk groups with distinct overall survival rates (P < 0.05, Kaplan-Meier analysis, log-rank tests). The 35-gene signature further stratified patients with clinical stage 1A diseases into poor prognostic and good prognostic subgroups (P = 0.0007, Kaplan-Meier analysis, log-rank tests). This signature is independent of other prognostic factors for non-small cell lung cancer, including age, sex, tumor differentiation, tumor grade, and tumor stage. The expression of the signature genes was validated with real-time RT-PCR analysis of lung cancer tumor specimens. Protein expression of two signature genes, TAL2 and ILF3, was confirmed in lung adenocarcinoma tumors by using Western blot analysis. These two biomarkers showed correlated mRNA and protein over-expression in lung cancer development and progression.
Conclusions
The results indicate that the identified 35-gene signature is an accurate predictor of survival in non-small cell lung cancer. It provides independent prognostic information in addition to traditional clinicopathological criteria.
doi:10.1158/1078-0432.CCR-08-0095
PMCID: PMC2605664  PMID: 19088038
molecular signature; non-small cell lung cancer; prognosis; microarray analysis; protein expression; Western blots
11.  AFAP120 regulates actin organization during neuronal differentiation 
During development, dynamic changes in the actin cytoskeleton determine both cell motility and morphological differentiation. In most mature tissues, cells are generally minimally motile and have morphologies specialized to their functions. In metastatic cancer, cells generally loose their specialized morphology and become motile. Therefore, proteins that regulate the transition between the motile and morphologically differentiated states can play important roles in determining cancer outcomes. AFAP120 is a neuronal specific protein that binds Src Kinase and Protein Kinase C (PKC) and cross-links actin filaments. Here we report that expression and tyrosine phosphorylation of AFAP120 are developmentally regulated in the cerebellum. In cerebellar cultures, PKC activation induces Src-kinase dependent phosphorylation of AFAP120, indicating that AFAP120 may be a downstream effector of Src. In neuroblastoma cells induced to differentiate by treatment with a PKC activator, tyrosine phosphorylation of AFAP120 appears to regulate the formation of the lamellar actin structures and subsequent neurite initiation. Together, these results indicate that AFAP120 plays a role in organizing dynamic actin structures during neuronal differentiation and suggest that AFAP120 may help regulate the transition from motile precursor to morphologically differentiated neurons.
doi:10.1016/j.diff.2008.09.006
PMCID: PMC2664250  PMID: 19281763
actin; AFAP; neuroblastoma; Src; neurite elongation
12.  Iron oxide nanoparticles induce human microvascular endothelial cell permeability through reactive oxygen species production and microtubule remodeling 
Background
Engineered iron nanoparticles are being explored for the development of biomedical applications and many other industry purposes. However, to date little is known concerning the precise mechanisms of translocation of iron nanoparticles into targeted tissues and organs from blood circulation, as well as the underlying implications of potential harmful health effects in human.
Results
The confocal microscopy imaging analysis demonstrates that exposure to engineered iron nanoparticles induces an increase in cell permeability in human microvascular endothelial cells. Our studies further reveal iron nanoparticles enhance the permeability through the production of reactive oxygen species (ROS) and the stabilization of microtubules. We also showed Akt/GSK-3β signaling pathways are involved in iron nanoparticle-induced cell permeability. The inhibition of ROS demonstrate ROS play a major role in regulating Akt/GSK-3β – mediated cell permeability upon iron nanoparticle exposure. These results provide new insights into the bioreactivity of engineered iron nanoparticles which can inform potential applications in medical imaging or drug delivery.
Conclusion
Our results indicate that exposure to iron nanoparticles induces an increase in endothelial cell permeability through ROS oxidative stress-modulated microtubule remodeling. The findings from this study provide new understandings on the effects of nanoparticles on vascular transport of macromolecules and drugs.
doi:10.1186/1743-8977-6-1
PMCID: PMC2632982  PMID: 19134195
13.  Podosomes and Invadopodia: Related structures with Common Protein Components that May Promote Breast Cancer Cellular Invasion 
Summary:
A rate-limiting step in breast cancer progression is acquisition of the invasive phenotype, which can precede metastasis. Expression of cell-surface proteases at the leading edge of a migrating cell provides cells with a mechanism to cross tissue barriers. A newly appreciated mechanism that may be relevant for breast cancer cell invasion is the formation of invadopodia, well-defined structures that project from the ventral membrane and promote degradation of the extracellular matrix, allowing the cell to cross a tissue barrier. Recently, there has been some controversy and discussion as to whether invadopodia, which are associated with carcinoma cells, are related to a similar structure called podosomes, which are associated with normal cells. Invadopodia and podosomes share many common characteristics, including a similar size, shape, subcellular localization and an ability to promote invasion. These two structures also share many common protein components, which we outline herein. It has been speculated that podosomes may be precursors to invadopodia and by extension both structures may be relevant to cancer cell invasion. Here, we compare and contrast the protein components of invadopodia and podosomes and discuss a potential role for these proteins and the evidence that supports a role for invadopodia and podosomes in breast cancer invasion.
PMCID: PMC3085414  PMID: 21655365
invadopodia; podosomes; invasion; breast cancer
14.  AFAP-110 is overexpressed in prostate cancer and contributes to tumorigenic growth by regulating focal contacts 
The Journal of Clinical Investigation  2007;117(10):2962-2973.
The actin filament–associated protein AFAP-110 is an actin cross-linking protein first identified as a substrate of the viral oncogene v-Src. AFAP-110 regulates actin cytoskeleton integrity but also functions as an adaptor protein that affects crosstalk between Src and PKC. Here we investigated the roles of AFAP-110 in the tumorigenic process of prostate carcinoma. Using immunohistochemistry of human tissue arrays, we found that AFAP-110 was absent or expressed at very low levels in normal prostatic epithelium and benign prostatic hyperplasia but significantly increased in prostate carcinomas. The level of AFAP-110 in carcinomas correlated with the Gleason scores. Downregulation of AFAP-110 in PC3 prostate cancer cells inhibited cell proliferation in vitro and tumorigenicity and growth in orthotopic nude mouse models. Furthermore, downmodulation of AFAP-110 resulted in decreased cell-matrix adhesion and cell migration, defective focal adhesions, and reduced integrin β1 expression. Reintroduction of avian AFAP-110 or a mutant disabling its interaction with Src restored these properties. However, expression of an AFAP-110 lacking the PKC-interacting domain failed to restore properties of parental cells. Thus, increased expression of AFAP-110 is associated with progressive stages of prostate cancer and is critical for tumorigenic growth, in part by regulating focal contacts in a PKC-dependent mechanism.
doi:10.1172/JCI30710
PMCID: PMC1978423  PMID: 17885682
15.  Cellular Pyrin Domain-Only Protein 2 Is a Candidate Regulator of Inflammasome Activation▿  
Infection and Immunity  2006;75(3):1484-1492.
Pyrin domain (PYD) proteins have recently emerged as important signaling molecules involved in the development of innate immunity against intracellular pathogens through activation of inflammatory mediator pathways. ASC is the central adaptor protein, which links pathogen recognition by PYD-containing pathogen recognition receptors, known as PYD-Nod-like receptors (NLR), PAN, PYPAF, NALP, Nod, and Caterpiller proteins, to the activation of downstream effectors, including activation of caspase-1 and NF-κB. Activation of these effectors occurs when specific protein complexes, known as inflammasomes, are formed. PYD signal transduction leads to inflammasome assembly and activation of specific effector proteins. It is modulated by a cellular PYD-only protein (cPOP1), which binds to ASC and interferes with the recruitment of ASC to activated PYD-NLRs. Here we describe the identification and characterization of a second cellular POP (cPOP2), which shows highest homology to the PYD of PAN1. cPOP2 binds to ASC and PAN1, thereby blocking formation of cryopyrin and PAN1-containing inflammasomes, activation of caspase-1, and subsequent processing and secretion of bioactive interleukin-1β. Existence of a second cPOP provides additional insights into inflammasome formation and suggests that POPs might be a common regulatory mechanism to “fine-tune” the activity of specific PYD-NLR family protein-containing inflammasomes.
doi:10.1128/IAI.01315-06
PMCID: PMC1828547  PMID: 17178784
16.  A novel role for 3, 4-dichloropropionanilide (DCPA) in the inhibition of prostate cancer cell migration, proliferation, and hypoxia-inducible factor 1alpha expression 
BMC Cancer  2006;6:204.
Background
The amide class compound, 3, 4-dichloropropionanilide (DCPA) is known to affect multiple signaling pathways in lymphocyte and macrophage including the inhibition of NF-κB ability. However, little is known about the effect of DCPA in cancer cells. Hypoxia-inducible factor 1 (HIF-1) regulates the expression of many genes including vascular endothelial growth factor (VEGF), heme oxygenase 1, inducible nitric oxide synthase, aldolase, enolase, and lactate dehydrogenase A. HIF-1 expression is associated with tumorigenesis and angiogenesis.
Methods
We used Transwell assay to study cell migration, and used immunoblotting to study specific protein expression in the cells.
Results
In this report, we demonstrate that DCPA inhibited the migration and proliferation of DU145 and PC-3 prostate cancer cells induced by serum, insulin, and insulin-like growth factor I (IGF-I). We found that DCPA inhibited HIF-1 expression in a subunit-specific manner in these cancer cell lines induced by serum and growth factors, and decreased HIF-1α expression by affecting its protein stability.
Conclusion
DCPA can inhibit prostate cancer cell migration, proliferation, and HIF-1α expression, suggesting that DCPA could be potentially used for therapeutic purpose for prostate cancer in the future.
doi:10.1186/1471-2407-6-204
PMCID: PMC1555598  PMID: 16884534
17.  Protein Kinase Cα Activates c-Src and Induces Podosome Formation via AFAP-110 
Molecular and Cellular Biology  2004;24(17):7578-7597.
We report that the actin filament-associated protein AFAP-110 is required to mediate protein kinase Cα (PKCα) activation of the nonreceptor tyrosine kinase c-Src and the subsequent formation of podosomes. Immunofluorescence analysis demonstrated that activation of PKCα by phorbol 12-myristate 13-acetate (PMA), or ectopic expression of constitutively activated PKCα, directs AFAP-110 to colocalize with and bind to the c-Src SH3 domain, resulting in activation of the tyrosine kinase. Activation of c-Src then directs the formation of podosomes, which contain cortactin, AFAP-110, actin, and c-Src. In a cell line (CaOV3) that has very little or no detectable AFAP-110, PMA treatment was unable to activate c-Src or effect podosome formation. Ectopic expression of AFAP-110 in CaOV3 cells rescued PKCα-mediated activation of c-Src and elevated tyrosine phosphorylation levels and subsequent formation of podosomes. Neither expression of activated PKCα nor treatment with PMA was able to induce these changes in CAOV3 cells expressing mutant forms of AFAP-110 that are unable to bind to, or colocalize with, c-Src. We hypothesize that one major function of AFAP-110 is to relay signals from PKCα that direct the activation of c-Src and the formation of podosomes.
doi:10.1128/MCB.24.17.7578-7597.2004
PMCID: PMC506973  PMID: 15314167
18.  PKC Phosphorylation Increases the Ability of AFAP-110 to Cross-link Actin Filaments 
Molecular Biology of the Cell  2002;13(7):2311-2322.
The actin filament-associated protein and Src-binding partner, AFAP-110, is an adaptor protein that links signaling molecules to actin filaments. AFAP-110 binds actin filaments directly and multimerizes through a leucine zipper motif. Cellular signals downstream of Src527F can regulate multimerization. Here, we determined recombinant AFAP-110 (rAFAP-110)-bound actin filaments cooperatively, through a lateral association. We demonstrate rAFAP-110 has the capability to cross-link actin filaments, and this ability is dependent on the integrity of the carboxy terminal actin binding domain. Deletion of the leucine zipper motif or PKC phosphorylation affected AFAP-110's conformation, which correlated with changes in multimerization and increased the capability of rAFAP-110 to cross-link actin filaments. AFAP-110 is both a substrate and binding partner of PKC. On PKC activation, stress filament organization is lost, motility structures form, and AFAP-110 colocalizes strongly with motility structures. Expression of a deletion mutant of AFAP-110 that is unable to bind PKC blocked the effect of PMA on actin filaments. We hypothesize that upon PKC activation, AFAP-110 can be cooperatively recruited to newly forming actin filaments, like those that exist in cell motility structures, and that PKC phosphorylation effects a conformational change that may enable AFAP-110 to promote actin filament cross-linking at the cell membrane.
doi:10.1091/mbc.E01-12-0148
PMCID: PMC117315  PMID: 12134071

Results 1-18 (18)