Electrical signals control wound healing through phosphatidylinositol-3-OH kinase-gamma and PTEN

Wound healing is essential for maintaining the integrity of multicellular organisms. In every species studied, disruption of an epithelial layer instantaneously generates endogenous electric fields, which have been proposed to be important in wound healing. The identity of signalling pathways that guide both cell migration to electric cues and electric-field-induced wound healing have not been elucidated at a genetic level. Here we show that electric fields, of a strength equal to those detected endogenously, direct cell migration during wound healing as a prime directional cue. Manipulation of endogenous wound electric fields affects wound healing in vivo. Electric stimulation triggers activation of Src and inositol-phospholipid signalling, which polarizes in the direction of cell migration. Notably, genetic disruption of phosphatidylinositol-3-OH kinase-gamma (PI(3)Kgamma) decreases electric-field-induced signalling and abolishes directed movements of healing epithelium in response to electric signals. Deletion of the tumour suppressor phosphatase and tensin homolog (PTEN) enhances signalling and electrotactic responses. These data identify genes essential for electrical-signal-induced wound healing and show that PI(3)Kgamma and PTEN control electrotaxis.     

Intramolecular reactions in the oxindole series

Zusammenfassung Es werden verschiedene Reaktionen in der Oxindolreihe diskutiert. Man kann sie sich als ?hnliche Mechanismen vorstellen, da alle über intramolekular gebildete Zwischenprodukte bzw. Endprodukte laufen.      

Properdin, the terminal complement components, thrombospondin and the circumsporozoite protein of malaria parasites contain similar sequence motifs

Properdin is a plasma glycoprotein which stabilizes the C3bnBb enzyme complex of the alternative pathway of the complement system. Unlike the classical pathway, which is initiated by interaction of C1q with the Fc regions of IgG or IgM antibodies in immune complexes, the alternative pathway can be directly activated via binding of C3b to surfaces of foreign organisms. The stabilized C3bnBbP complex activates components C3 and C5 resulting in opsonization of foreign material (via C3b) and assembly of the membrane attack complex (via C5b) on target cells. Therefore properdin greatly enhances complement-mediated clearance and inactivation mechanisms in both natural and acquired resistance to infection. This paper shows that the primary amino acid sequence of properdin is composed mainly of six repeating motifs, each of approximately 60 amino acids, and that similar sequences are found in thrombospondin, the circumsporozoite protein of malaria parasites and regions of the membrane-attack components of complement. These similarities may provide insight into the mechanisms by which parasites avoid host defences mediated by complement.     

Frequent somatic mutations in MAP3K5 and MAP3K9 in metastatic melanoma identified by exome sequencing

We sequenced eight melanoma exomes to identify new somatic mutations in metastatic melanoma. Focusing on the mitogen-activated protein (MAP) kinase kinase kinase (MAP3K) family, we found that 24% of melanoma cell lines have mutations in the protein-coding regions of either MAP3K5 or MAP3K9. Structural modeling predicted that mutations in the kinase domain may affect the activity and regulation of these protein kinases. The position of the mutations and the loss of heterozygosity of MAP3K5 and MAP3K9 in 85% and 67% of melanoma samples, respectively, together suggest that the mutations are likely to be inactivating. In in vitro kinase assays, MAP3K5 I780F and MAP3K9 W333* variants had reduced kinase activity. Overexpression of MAP3K5 or MAP3K9 mutants in HEK293T cells reduced the phosphorylation of downstream MAP kinases. Attenuation of MAP3K9 function in melanoma cells using siRNA led to increased cell viability after temozolomide treatment, suggesting that decreased MAP3K pathway activity can lead to chemoresistance in melanoma.     

NHE3 phosphorylation via PKCη marks the polarity and orientation of directionally migrating cells

Endogenous electric fields (EF) may provide an overriding cue for directional cell migration during wound closure. Perceiving a constant direction requires active sodium-hydrogen exchanger (pNHE3) at the leading edge of HEK 293 cells but its activation mechanism is not yet fully understood. Because protein kinase C (PKC) is required in electrotaxis, we asked whether NHE3 is activated by PKC during wound healing. Using pharmacological (pseudosubstrate and edelfosine) inhibition, we showed that inhibition of PKCη isoform impairs directional cell migration in HEK 293 cells in the presence of a persistent directional cue (0.25–0.3 V/mm of EF for 2 h). Further, we found that pNHE3 forms complexes with both PKCη and ?-tubulin, suggesting that these molecules may regulate the microtubule-organizing center. In addition, cellular pNHE3 content was reduced significantly when PKCη was inhibited during directional cell migration. Taken together, these data suggest that PKCη-dependent phosphorylation of NHE3 and the formation of pNHE3/PKCη/?-tubulin complexes at the leading edge of the cell are required for directional cell migration in an EF.     

Pathogenesis of skin ulcers: lessons from the Mycobacterium ulcerans and Leishmania spp. pathogens

Skin ulcers are most commonly due to circulatory or metabolic disorders and are a major public health concern. In developed countries, chronic wounds affect more than 1 % of the population and their incidence is expected to follow those observed for diabetes and obesity. In tropical and subtropical countries, an additional issue is the occurrence of ulcers of infectious origins with diverse etiologies. While the severity of cutaneous Leishmaniasis correlates with protective immune responses, Buruli ulcers caused by Mycobacterium ulcerans develop in the absence of major inflammation. Based on these two examples, this review aims to demonstrate how studies on microorganism-provoked wounds can provide insight into the molecular mechanisms controlling skin integrity. We highlight the potential interest of a mouse model of non-inflammatory skin ulceration caused by intradermal injection of mycolactone, an original lipid toxin with ulcerative and immunosuppressive properties produced by M. ulcerans.