<p> DER, the Drosophila Epidermal Growth Factor Receptor (DEgfr) is the only known fly orthologue of vertebrate Neu/ErbB2 receptor tyrosine kinase family. Receptor Tyrosine Kinases (RTKs) like DER and ErbB2 play an important role in regulating cell differentiation, cell proliferation and cell survival in metazoan animals. Neu/ErbB2 is over-expressed in 20-30% human breast cancers, which correlates with poor clinical prognosis in cancer patients. </p> <p> Our previous studies showed that rat-NeriJErbB2 could successfully signal in vivo using Drosophila adaptor and second messenger molecules. Here we regenerated the transgenic fly lines with various neu add-back alleles. We further re-established mis-expression phenotypes in various adult structures such as wings and eyes, the tissues known to require DEgfr signaling. By using genetic approach, we have demonstrated that the tyrosine residue at the 1028 site (NeuYA), might have an inhibitory role in RTK signaling. In addition we have already generated a number of double add-back neu alleles where tyrosine site at the 1028 site (neuYA) was added back to another Neu allele and made neuYAB, neuYAc neuYAD and neuYAE. Transgenic flies with these alleles will be generated to further study the inhibitory role of Neu^YA. </p> <p> Finally, our on going large-scale genetic screening is likely to reveal the component(s) of NeuYE (Y1253) pathway that does not utilize the function of Ras. </p> / Thesis / Master of Science (MSc)

The Neu/ErbB2 receptor tyrosine kinase has been implicated in the induction of mammary tumourigenesis. Both Ras-dependent and independent signalling downstream of activated Neu is believed to mediate cellular signalling that contributes cellular transformation in oncogenic Neu. Signalling from five 𝘣𝘰𝘯𝘢 𝘧𝘪𝘥𝘦 autophosphorylation sites (termed sites A through E) in the carboxyl tail of the receptor mediate these signals to the cytosol. Of the four positive regulatory sites (B, C, D, E), only three (B, C, D,) signal through known signalling molecules. Site E, (Y1253) in Neu, though known to interact with DOKR is essentially an orphan site. The discovery of a 34kD protein capable of associating to peptides corresponding to site E prompted investigations into the nature of site E signalling. Mass spectrometric analyses revealed that the 34kD protein is 2,4-dienoyl-CoA reductase (DECR1), a lipid metabolism protein typically localized to the mitochondria. Investigations into this protein reveal that DECR1 is capable of associating with Neu site E in a tyrosine phosphorylation and sequence specific manner. Furthermore, analyses with site E second-site mutants (YE[APEY], YE[DPEY], YE[NAEY] and YE[NDEY]) show that DECR1 associates in a manner consistent to a PTB domain-containing protein. Analyses of amino acid sequence demonstrate the presence of a putative Bcl-domain in DECR1 suggestive of a role in apoptosis. Experiments into the apoptotic activity of DECR1 proved inconclusive. The examination of sub-cellular localization of Neu and DECR1 showed that the two proteins are found in both the mitochondrial and plasma membrane fractions. These results demonstrate that DECR1 may be a veritable binding partner for Neu Y1253. / Thesis / Master of Science (MSc)

La dimérisation induite par la fixation de ligand est nécessaire à l'activation des récepteurs tyrosine kinase. Le domaine transmembranaire unique de ces protéines joue un rôle crucial dans ces mécanismes. Le récepteur Neu chez le rat et son homologue ErbB2 chez l'humain sont à l'origine de nombreux cancers provoqués par la mutation ponctuelle Val/Glu dans le segment transmembranaire ou la surexpression du récepteur. La structure du domaine transmembranaire dans le récepteur dimère semble déterminante dans les processus d'activation. Les simulations de dynamique moléculaire montrent que, dans une membrane modèle constituée de DMPC ou de POPC hydratés, les hélices transmembranaires de Neu sauvage et oncogénique s'associent préférentiellement en enroulement gauche formant une interface symétrique. Dans le cas de Neu oncogénique le résidu polaire Glu, enfoui dans la membrane, stabilise les interactions entre hélices en formant de fortes liaisons hydrogène