Phosphorylation of ribosomal protein S6 during lens cell differentiation: correlation with translational efficiency

Signal transduction pathways in macroautophagy

Macroautophagy is a major cellular catabolic pathway involved in the regulation of cell homeostasis. It is initiated by the sequestration of intracellular material by a wrapping membrane and terminates with the fusion of autophagic vacuoles with the lysosomal compartment. Macroautophagy has been extensively studied at the morphological level and in terms of environmental responses (nutrient deprivation, hormones). Recently a burst of data has emerged concerning the intracellular molecular events involved in the control of macroautophagic sequestration. It is becoming clear that the initial sequestration step of macroautophagy is under the control of different signalling pathways.

Identification of receptor tyrosine kinases in the embryonic chicken lens

Protein phosphorylation plays a critical role in the control of growth and regulation of many eukaryotic cells. Members of the protein tyrosine kinase (PTK) family of peptides function as growth factor receptors and oncoproteins. A common feature of members of the PTK family is a highly conserved intracellular catalytic domain. We analyzed the chicken lens epithelium, which responds to several known growth factors, for the presence of receptor PTK's. Using reverse transcription polymerase chain reaction (rtPCR) and degenerate primers made to conserved regions within kinase domains, we amplified RNA from embryonic day 6 (E6) lens epithelium and sequenced 135 cDNA clones. Sixteen distinct kinase sequences were obtained. Eight of these sequences represented kinase domains of known mammalian growth factor receptors, and six represented intercellular kinases. Two sequences appeared to code for new kinases. The amino acid identity of the chicken homologs ranged from 80-100% when compared to their mammalian counterparts.