Protein kinase-like domains that lack conserved residues known to catalyse phosphoryl transfer, termed pseudokinases, have emerged as important signalling domains across all kingdoms of life. Although predicted to function principally as catalysis-independent protein-interaction modules, several pseudokinase domains have been attributed unexpected catalytic functions, often amid controversy. We established a thermal-shift assay as a benchmark technique to define the nucleotide-binding properties of kinase-like domains. Unlike in vitro kinase assays, this assay is insensitive to the presence of minor quantities of contaminating kinases that may otherwise lead to incorrect attribution of catalytic functions to pseudokinases. We demonstrated the utility of this method by classifying 31 diverse pseudokinase domains into four groups: devoid of detectable nucleotide or cation binding; cation-independent nucleotide binding; cation binding; and nucleotide binding enhanced by cations. Whereas nine pseudokinases bound ATP in a divalent cation-dependent manner, over half of those examined did not detectably bind nucleotides, illustrating that pseudokinase domains predominantly function as non-catalytic protein-interaction modules within signalling networks and that only a small subset is potentially catalytically active. We propose that henceforth the thermal-shift assay be adopted as the standard technique for establishing the nucleotide-binding and catalytic potential of kinase-like domains.

Summary Integrin-linked kinase (ILK) plays a pivotal role in connecting transmembrane receptor integrin to the actin cytoskeleton and thereby regulating diverse cell adhesion-dependent processes. The kinase domain (KD) of ILK is indispensable for its function, but the underlying molecular basis remains enigmatic. Here we present the crystal structure of the ILK KD bound to its cytoskeletal regulator, the C-terminal calponin homology domain of α-parvin. While maintaining a canonical kinase fold, the ILK KD displays a striking pseudo-active site conformation. We show that rather than performing the kinase function, this conformation specifically recognizes α-parvin for promoting effective assembly of ILK into focal adhesions. The α-parvin-bound ILK KD can simultaneously engage integrin β cytoplasmic tails. These results thus define ILK as a distinct pseudokinase that mechanically couples integrin and α-parvin for mediating cell adhesion. They also highlight functional diversity of the kinase fold and its “active” site in mediating many biological processes.

Integrin-mediated cell-matrix adhesion plays an important role in control of cell behavior. We report here that MIG-2, a widely expressed focal adhesion protein, interacts with ␤1 and ␤3 integrin cytoplasmic domains. Integrin binding is mediated by a single site within the MIG-2 FERM domain. Functionally, the MIG-2/integrin interaction recruits MIG-2 to focal adhesions. Furthermore, using ␣IIb␤3 integrin-expressing Chinese hamster ovary cells, a well described model system for integrin activation, we show that MIG-2 promotes integrin activation and enhances cell-extracellular matrix adhesion. Although MIG-2 is expressed in many cell types, it is deficient in certain colon cancer cells. Expression of MIG-2, but not of an integrin binding-defective MIG-2 mutant, in MIG-2-null colon cancer cells strengthened cell-matrix adhesion, promoted focal adhesion formation, and reduced cell motility. These results suggest that the MIG-2/integrin interaction is an important element in the cellular control of integrin-mediated cell-matrix adhesion and that loss of this interaction likely contributes to high motility of colon cancer cells.Cell-extracellular matrix (ECM) 3 adhesion is a fundamental process that is mediated by transmembrane receptors such as integrins (1-6). The interactions of integrins with ECM ligands can be controlled by integrin activation via "inside-out" signaling. Talin, a FERM (Band 4.1 (four point one)/ezrin/radixin/ moesin) domain-containing focal adhesion (FA) protein, can play a key role in this process (for recent reviews, see Refs. 7-10). Binding of the talin FERM domain to the ␤ integrin cytoplasmic domains results in separation of the ␣ and ␤ integrin cytoplasmic tails and consequently in an increase in integrin extracellular ligand-binding affinity (i.e. integrin activation) (11-13). Integrin extracellular ligand-binding affinity plays an important role in control of initial cell-ECM adhesion. Additionally, integrin-mediated cell-ECM adhesion can be enhanced through interactions with cytoskeletal proteins, a process that has been termed cytoskeletal strengthening (14 -16). The physical basis underlying the cytoskeletal strengthening of cell-ECM adhesion has been well described (16). However, the molecular interactions that mediate this process remain to be defined.MIG-2 (mitogen-inducible gene-2, also known as kindlin-2) is a widely expressed and evolutionarily conserved cytoplasmic protein (17-21). Genetic studies have shown that Caenorhabditis elegans UNC-112, a homolog of MIG-2, is required for attachment of body-wall muscle cells to the hypodermis (17,19). Loss of UNC-112 in C. elegans results in an embryonic lethal Pat (paralyzed, arrested elongation at two-fold) phenotype resembling that of ␣ or ␤ integrin loss (17, 19). In mammalian organisms, MIG-2 has been detected in many cell types, including fibroblasts, muscle cells, endothelial cells, and epithelial cells (20,22). In these cells, it concentrates at FAs. MIG-2 interacts with migfilin (20), a filamin-and VASP (vasodilatorstimulated p...

Accurate identification of aspermic Fasciola forms in Japan remains difficult because of their morphological variations. In order to characterize the forms genetically, nucleotide sequences of ribosomal internal transcribed spacer (ITS1 and ITS2) and mitochondrial cytochrome c oxidase I (COI) and NADH dehydrogenase I (NDI) genes in 34 liver flukes from 16 prefectures in Japan were analysed. Two major forms represented by Fsp 1 and Fsp 2 had sequences identical to or closely resembling those of F. hepatica and F. gigantica, respectively, in all the 4 DNA markers and were mainly distributed in northern and eastern-western parts of Japan, respectively. Fsp 1 and Fsp 2 would have been introduced into Japan with infected cattle of 2 distinct lineages via the Korean Peninsula and spread through limited parts of Japan (northern and eastern-western parts) together with the movement of each cattle lineage. The Japanese form (Fsp 1/2), which showed heterozygosity in ribosomal DNA and Fsp 2 haplotype in mitochondrial DNA, may have originated in interspecific cross hybridization between paternal F. hepatica and maternal F. gigantica.

The membrane localization and activation of cytoskeletal protein talin are key steps to initiate integrin transmembrane receptors activation, which mediates many cellular adhesive responses such as cell migration, spreading, and proliferation. RIAM, a membrane anchor and small GTPase RAP1 effector, is known to bind to the C-terminal rod domain of talin (talin-R) and promote localizations of talin to membrane. Through systematic mapping analysis, we find that RIAM also binds to the N-terminal head of talin (talin-H), a crucial domain involved in binding and activating integrins. We show that the RIAM binding to talin-H sterically occludes the binding of a talin-R domain that otherwise masks the integrin binding site on talin-H. We further provide functional evidence that such RIAM-mediated steric unmasking of talin triggers integrin activation. Our findings thus uncover a novel role for RIAM in conformational regulation of talin during integrin activation and cell adhesion.

Toll-like receptors transduce their signals through the adaptor molecule MyD88 and members of the IL-1R-associated kinase family (IRAK-1, 2, M and 4). IRAK-1 and IRAK-2, known to form Myddosomes with MyD88-IRAK-4, mediate TLR7-induced TAK1-dependent NFjB activation. IRAK-M was previously known to function as a negative regulator that prevents the dissociation of IRAKs from MyD88, thereby inhibiting downstream signalling. However, we now found that IRAK-M was also able to interact with MyD88-IRAK-4 to form IRAK-M Myddosome to mediate TLR7-induced MEKK3-dependent second wave NFjB activation, which is uncoupled from post-transcriptional regulation. As a result, the IRAK-M-dependent pathway only induced expression of genes that are not regulated at the post-transcriptional levels (including inhibitory molecules SOCS1, SHIP1, A20 and IjBa), exerting an overall inhibitory effect on inflammatory response. On the other hand, through interaction with IRAK-2, IRAK-M inhibited TLR7-mediated production of cytokines and chemokines at translational levels. Taken together, IRAK-M mediates TLR7-induced MEKK3-dependent second wave NFjB activation to produce inhibitory molecules as a negative feedback for the pathway, while exerting inhibitory effect on translational control of cytokines and chemokines.

Abstract-Corin is a cardiac serine protease that acts as the pro-atrial natriuretic peptide (ANP) convertase. Recently, 2 single-nucleotide polymorphisms (SNPs) (T555I and Q568P) in the human corin gene have been identified in genetic epidemiological studies. The minor I555/P568 allele, which is more common in African Americans, is associated with hypertension and cardiac hypertrophy. In this study, we examined the effect of T555I and Q568P amino acid substitutions on corin function. We found that corin frizzled-like domain 2, where T555I/Q568P substitutions occur, was required for efficient pro-ANP processing in functional assays. Mutant corin lacking this domain had 30Ϯ5% (PϽ0.01) activity compared to that of wild type. Similarly, corin variant T555I/Q568P had a reduced (38Ϯ7%, PϽ0.01) pro-ANP processing activity compared to that of wild type. The variant also exhibited a low activity (44Ϯ15%, PϽ0.05) in processing pro-brain natriuretic peptide (BNP). We next examined the biochemical basis for the loss of activity in T555I/Q568P variant and found that the zymogen activation of the corin variant was impaired significantly, as indicated by the absence of the activated protease domain fragment. This finding was confirmed in human embryonic kidney (HEK)293 cells and murine HL-1 cardiomyocytes. Thus, our results show that the corin gene SNPs associated with hypertension and cardiac hypertrophy impair corin zymogen activation and natriuretic peptide processing activity. Our data suggest that corin deficiency may be an important mechanism in hypertensive and heart diseases. (Circ Res. 2008;103:502-508.)Key Words: natriuretic peptides Ⅲ genetic variants Ⅲ protease A trial natriuretic peptide (ANP) is a cardiac hormone that regulates blood pressure and salt-water balance. 1-3 The ANP pathway also has an antihypertrophic function in the heart, which is independent of its systemic action on blood pressure. 4 -7 Corin is a cardiac enzyme of the type II transmembrane serine protease family. 8 -10 It has a cytoplasmic tail and a transmembrane domain near the N terminus. In its extracellular region, there are 2 frizzled-like domains, 8 LDL receptor (LDLR) repeats, a scavenger receptor-like domain, and a C-terminal trypsin-like protease domain. Corin converts pro-ANP into active ANP. 11,12 In mice, corin deficiency prevented pro-ANP activation, 13 demonstrating that corin is the physiological pro-ANP convertase. Corin-null mice developed hypertension and cardiac hypertrophy. 13 Corin also cleaved pro-brain natriuretic peptide (BNP) in vitro, although the cleavage was less efficient than that for pro-ANP. 12 Hypertension is the most common cardiovascular disease, and its prevalence is even higher in African Americans, but the underlying mechanism is unclear. 14,15 Recently, 2 nonsynonymous and nonconservative single-nucleotide polymorphisms (SNPs) (T555I and Q568P) are found in the human corin gene. These 2 SNPs are in complete linkage disequilibrium in the population and, as a result, are colocalized in a minor allele (I555...

Background: Kindlin-2 is a key regulator of integrin activation. Results: Kindlin-2 contains a PH domain with a distinct binding pocket for phosphatidylinositol-(3,4,5)-trisphosphate (PIP3) that promotes talin-mediated integrin activation. Conclusion: PIP3-mediated membrane binding of kindlin-2 is crucial for the cooperation of kindlin-2 with talin in activating integrin. Significance: Learning how kindlin-2 functions is crucial for understanding the integrin-mediated cell adhesion.