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S J Madigan

Publications and source records attributed to S J Madigan.

8 recordsLinked to original sources
PubMed1999

DFak56 is a novel Drosophila melanogaster focal adhesion kinase.

The mammalian focal adhesion kinase (FAK) family of nonreceptor protein-tyrosine kinases have been implicated in controlling a multitude of cellular responses to the engagement of cell surface integrins and G protein-coupled receptors. We describe here a Drosophila melanogaster FAK homologue, DFak56, which maps to band 56D on the right arm of the second chromosome. Full-length DFak56 cDNA encodes a phosphoprotein of 140 kDa, which shares strong sequence similarity not only with mammalian p125(FAK) but also with the more recently described mammalian Pyk2 (also known as CAKbeta, RAFTK, FAK2, and CADTK) FAK family member. DFak56 has intrinsic tyrosine kinase activity and is phosphorylated on tyrosine in vivo. As is the case for FAK, tyrosine phosphorylation of DFak56 is increased upon plating Drosophila embryo cells on extracellular matrix proteins. In situ hybridization and immunofluorescence staining analysis showed that DFak56 is ubiquitously expressed with particularly high levels within the developing central nervous system. We utilized the UAS-GAL4 expression system to express DFak56 and analyze its function in vivo. Overexpression of DFak56 in the wing imaginal disc results in wing blistering in adults, a phenotype also observed with both position-specific integrin loss of function and position-specific integrin overexpression. Our results imply a role for DFak56 in adhesion-dependent signaling pathways in vivo during D. melanogaster development.

Amino Acid Sequence↗
PubMed1998

pcdr, a novel gene with sexually dimorphic expression in the pigment cells of the Drosophila eye.

We report the molecular cloning and characterization of pcdr (pigment cell dehydrogenase reductase), a Drosophila visual system-specific gene with novel properties of spatial, temporal and sexual regulation. Short chain dehydrogenase/reductases are a family of proteins that catalyze mechanistically conserved dehydrogenase/reductase reactions in a wide range of cells and tissues. These enzymes are required in a variety of reactions ranging from steroid metabolism and prostaglandin synthesis to alcohol detoxification. The Drosophila pcdr gene encodes a new member of this family, displaying 42% amino acid sequence identity to the mammalian prostaglandin dehydrogenase. pcdr expression is restricted to the visual system with very high levels found in the pigment cells. Interestingly, expression of pcdr mRNA is sexually dimorphic with males showing higher levels of expression than females. This sexual dimorphism is under the control of the sex differentiation cascade as transformer and transformer 2 mutations shift females to a male-like level of expression. Finally, we demonstrate that a region of 335 nucleotides including sequences upstream and just downstream of the transcription start is sufficient to reproduce the normal expression pattern.

Amino Acid Sequence↗
PubMed1996

att, a target for regulation by tra2 in the testes of Drosophila melanogaster, encodes alternative RNAs and alternative proteins.

We have identified a gene, alternative testis transcripts (att), which is alternatively expressed, at both the RNA and protein levels, in testes and somatic tissues. The testis-specific RNA differs from somatic RNAs in both promoter usage and RNA processing and is dependent on the function of the transformer 2 gene. The differences between the somatic and testis RNAs have substantial consequences at the protein level. The somatic RNAs encode a protein with homology to the mammalian Graves' disease carrier proteins. The testis RNA lacks the initiation codons used in somatic tissue and encodes two different proteins. One of these begins in a testis-specific exon, uses a reading frame different from that for the somatic protein, and is completely novel. The other protein initiates translation in the frame of the somatic RNA at a Len CUG codon which is within the open reading frame for the somatic protein. This produces a novel truncated version of the Graves' disease carrier protein-like protein that lacks all sequences N terminal to the first transmembrane domain.

Alternative Splicing↗
PubMed1994

Multiple portions of a small region of the Drosophila transformer gene are required for efficient in vivo sex-specific regulated RNA splicing and in vitro sex-lethal binding.

The transformer gene of Drosophila is regulated by Sex-lethal-dependent 3' splice site blockage. 40 nucleotides immediately upstream of the regulated splice site are sufficient to direct sex-specific regulated splicing in transgenic animals. This entire region appears to be necessary for regulation and for efficient Sex-lethal binding. Natural splice sites containing partial homology to transformer do not show regulation. Mutations which replace the 16 nucleotides surrounding the branch point or alter single nucleotides near the splice site eliminate or reduce regulation without eliminating splicing. Mutations which reduce or eliminate regulation in vivo reduce binding to Sex-lethal in vitro, consistent with the hypothesis that these mutations bring about their effects by altering Sex-lethal binding rather than by altering binding sites for additional non-Sex-lethal factors.

Animals↗
PubMed1990

Sterol phylogenesis and algal evolution.

The stereochemistry of several sterol precursors and end products synthesized by two fungal-like micro-organisms Prototheca wickerhamii (I) and Dictyostelium discoideum (II) have been determined by chromatographic (TLC, GLC, and HPLC) and spectral (UV, MS, and 1H NMR) methods. From I and II the following sterols were isolated from the cells: cycloartenol, cyclolaudenol, 24(28)-methylenecycloartanol, ergosterol, protothecasterol, 4alpha-methylergostanol, 4alpha-methylclionastanol, clionastanol, 24beta-ethylcholesta-8,22-enol, and dictyosterol. In addition, the mechanism of C-24 methylation was investigated in both organisms by feeding to I [2-3H]lanosterol, [2-3H]cycloartenol, [24-3H]lanosterol, and [methyl-2H3]methionine and by feeding to II [methyl-2H3]methionine. The results demonstrate that the 24beta configuration is formed by different alkylation routes in I and II. The Delta25(27) route operates in I while the Delta24(28) route operates in II. Based on what is known in the literature regarding sterol distribution and phylogenesis together with our findings that the stereochemical outcome of squalene oxide cyclization leads to the production of cycloartenol rather than lanosterol (characteristic of the fungal genealogy) and the chirality of the C-24 alkyl group is similar in the two nonphotosynthetic microbes (beta oriented), we conclude that Prototheca is an apoplastic Chlorella (i.e., an alga) and that Dictyostelium as well as the other soil amoebae that synthesize cycloartenol evolved from algal rather than fungal ancestors.

Journal Article↗
PubMed1989

Identification and characterization of catA, a mutation causing catalase deficiency in Dictyostelium discoideum.

Various strains of Dictyostelium discoideum were assayed for catalase activity. We were able to demonstrate the presence of catalase in lysates of all strains tested except one, ts12m. Lysates of this strain did not show any detectable level of catalase. The increased sensitivity of intact ts12m amoebae to hydrogen peroxide was consistent with the catalase deficiency. We followed catalase activity through a developmental time course for the wild type (Ddb) and were able to show its presence throughout development. No catalase activity was detected from ts12m in any stage of development. The growth and development of this acatalasemic strain of D. discoideum was no different than those of the wild type. The mutation, catA, was assigned to linkage group II.

Catalase↗