Genetic screens for dominant second-site mutations that suppress the lethality of Abl mutations in Drosophila identified alleles of only one gene, enabled (ena). We report that the ena protein contains proline-rich motifs and binds to Abl and Src SH3 domains, ena is also a substrate for the Abl kinase; tyrosine phosphorylation of ena is increased when it is coexpressed in cells with human or Drosophila Abl and endogenous ena tyrosine phosphorylation is reduced in Abl mutant animals. Like Abl, ena is expressed at highest levels in the axons of the embryonic nervous system and ena mutant embryos have defects in axonal architecture. We conclude that a critical function of Drosophila Abl is to phosphorylate and negatively regulate ena protein during neural development.

Extracellular matrix proteins and proteins involved in epithelial adhesion are essential for maintenance of tissue structure. Helicobacter pylori is the major aetiological agent in peptic ulcer disease and has been shown to increase gastric cancer risk up to ninefold. In this study, changes induced by H pylori on the expression of extracellular matrix proteins (collagen IV, fibronectin, and laminin) as well as two essential proteins for cell-basement and cell-cell adhesion ( 6-integrin and E-cadherin) were assessed. Immunohistochemistry was performed in antral biopsy sections obtained from infected and non-infected patients, and light microscopy was used to determine the distribution and intensity of specific staining. The results showed that the infection was significantly associated with downregulation of E-cadherin, an essential protein for maintenance of solid tissues and diVerentiation, but did not induce changes in the expression of 6-integrin or the extracellular matrix proteins. (J Clin Pathol 1998;51:410-412)

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