Faculty Bibliography

The prevention of new blood vessel growth is an increasingly attractive strategy to limit tumor growth. However, it remains unclear whether anti-angiogenesis approaches will impair wound healing, a process thought to be angiogenesis dependent. Results of previous studies differ as to whether angiogenesis inhibitors delay wound healing. We evaluated whether endostatin at tumor-inhibiting doses delayed excisional wound closure. C57/BL6J mice were treated with endostatin or phosphate-buffered solution 3 days prior to the creation of two full-thickness wounds on the dorsum. Endostatin was administered daily until wound closure was complete. A third group received endostatin, but also had daily topical vascular endothelial growth factor applied locally to the wound. Wound area was measured daily and the wounds were analyzed for granulation tissue formation, epithelial gap, and wound vascularity. Endostatin-treated mice showed a significant delay in wound healing. Granulation tissue formation and wound vascularity were significantly decreased, but reepithelialization was not effected. Topical vascular endothelial growth factor application to wounds in endostatin-treated mice resulted in increased granulation tissue formation, increased wound vascularity, and wound closure approaching that of control mice. This study shows that the angiogenesis inhibitor endostatin delays wound healing and that topical vascular endothelial growth factor is effective in counteracting this effect

The cell biologist's insight into endosomal diversity, in terms of both form and function, has increased dramatically in the past few years. This understanding has been promoted by the availability of powerful new techniques that allow imaging of both cargo and machinery in the endocytic process in real time, and by our ability to inhibit components of this machinery by RNA interference. The emerging picture from these studies is of a highly complex, dynamic and adaptable endosomal system that interacts at various points with the secretory system of the cell.

Invasive cell migration in both normal development and metastatic cancer is regulated by various signaling pathways, transcription factors and cell-adhesion molecules. The coordination between these activities in the context of cell migration is poorly understood. During Drosophila oogenesis, a small group of cells called border cells exit the follicular epithelium to perform a stereotypic, invasive migration. We find that the ETS transcription factor Yan is required for border cell migration and that Yan expression is spatiotemporally regulated as border cells migrate from the anterior pole of the egg chamber towards the nurse cell-oocyte boundary. Yan expression is dependent on inputs from the JAK/STAT, Notch and Receptor Tyrosine Kinase pathways in border cells. Mechanistically, Yan functions to modulate the turnover of DE-Cadherin-dependent adhesive complexes to facilitate border cell migration. Our results suggest that Yan acts as a pivotal link between signal transduction, cell adhesion and invasive cell migration in Drosophila border cells

Germ cells must develop along distinct male or female paths to produce the sperm or eggs required for sexual reproduction. In both mouse and Drosophila, the sexual identity of germ cells is influenced by the sex of the surrounding somatic tissue (for example, refs 1, 2, reviewed in refs 3, 4); however, little is known about how the soma controls germline sex determination. Here we show that the janus kinase/signal transducer and activator of transcription (JAK/STAT) pathway provides a sex-specific signal from the soma to the germ line in Drosophila embryonic gonads. The somatic gonad expresses a JAK/STAT ligand, unpaired (upd), in a male-specific manner, and activates the JAK/STAT pathway in male germ cells at the time of gonad formation. Furthermore, the JAK/STAT pathway is necessary for male-specific germ cell behaviour during early gonad development, and is sufficient to activate aspects of male germ cell behaviour in female germ cells. Our findings provide direct evidence that the JAK/STAT pathway mediates a key signal from the somatic gonad that regulates male germline sexual development.

BACKGROUND: It is known that 5-lipoxygenase and its product, leukotriene B4 (LTB4), are highly expressed in several human pathologies, including atherosclerotic plaque. LTB(4) signals primarily through its high-affinity G protein-coupled receptor BLT1, which is expressed on specific leukocyte subsets. BLT1 receptor expression and function on other atheroma-associated cell types is unknown. METHODS AND RESULTS: To directly assess the role of the LTB4-BLT1 pathway in atherogenesis, we bred BLT1(-/-) mice into the atherosclerosis-susceptible apoE(-/-) strain. Compound-deficient apoE(-/-)/Blt1(-/-) mice fed a Western-type diet had a marked reduction in plaque formation compared with apoE(-/-) controls. Immunohistochemical analysis of atherosclerotic lesions in compound-deficient mice revealed a striking decrease in smooth muscle cells (SMCs) and significant decreases in macrophages and T cells. We report here novel evidence of the expression and function of BLT1 on vascular SMCs. LTB4 triggered SMC chemotaxis, which was pertussis toxin sensitive in Blt1(+/+) SMCs and absent in Blt1(-/-) cells, suggesting that BLT1 was the dominant receptor mediating effector functions through a G protein-coupled signaling pathway. Furthermore, BLT1 colocalized with SMCs in human atherosclerotic lesions. CONCLUSIONS: These new findings extend the role of inducible BLT1 to nonleukocyte populations and suggest an important target for intervention to modulate the response to vascular injury

The hallmarks of telomere dysfunction in mammals are reduced telomeric 3' overhangs, telomere fusions, and cell cycle arrest due to a DNA damage response. Here, we report on the phenotypes of RNAi-mediated inhibition of POT1, the single-stranded telomeric DNA-binding protein. A 10-fold reduction in POT1 protein in tumor cells induced neither telomere fusions nor cell cycle arrest. However, the 3' overhang DNA was reduced and all telomeres elicited a transient DNA damage response in G1, indicating that extensive telomere damage can occur without cell cycle arrest or telomere fusions. RNAi to POT1 also revealed its role in generating the correct sequence at chromosome ends. The recessed 5' end of the telomere, which normally ends on the sequence ATC-5', was changed to a random position within the AATCCC repeat. Thus, POT1 determines the structure of the 3' and 5' ends of human chromosomes, and its inhibition generates a novel combination of telomere dysfunction phenotypes in which chromosome ends behave transiently as sites of DNA damage, yet remain protected from nonhomologous end-joining

We present analysis, by cryo-electron microscopy and single-particle reconstruction, of the structure of the 80S ribosome from Trypanosoma cruzi, the kinetoplastid protozoan pathogen that causes Chagas disease. The density map of the T. cruzi 80S ribosome shows the phylogenetically conserved eukaryotic rRNA core structure, together with distinctive structural features in both the small and large subunits. Remarkably, a previously undescribed helical structure appears in the small subunit in the vicinity of the mRNA exit channel. We propose that this rRNA structure likely participates in the recruitment of ribosome onto the 5' end of mRNA, in facilitating and modulating the initiation of translation that is unique to the trypanosomes

Palmitoylation is postulated to regulate Ras signaling by modulating its intracellular trafficking and membrane microenvironment. The mechanisms by which palmitoylation contributes to these events are poorly understood. Here, we show that dynamic turnover of palmitate regulates the intracellular trafficking of HRas and NRas to and from the Golgi complex by shifting the protein between vesicular and nonvesicular modes of transport. A combination of time-lapse microscopy and photobleaching techniques reveal that in the absence of palmitoylation, GFP-tagged HRas and NRas undergo rapid exchange between the cytosol and ER/Golgi membranes, and that wild-type GFP-HRas and GFP-NRas are recycled to the Golgi complex by a nonvesicular mechanism. Our findings support a model where palmitoylation kinetically traps Ras on membranes, enabling the protein to undergo vesicular transport. We propose that a cycle of depalmitoylation and repalmitoylation regulates the time course and sites of Ras signaling by allowing the protein to be released from the cell surface and rapidly redistributed to intracellular membranes