Immunochemical localization of the phylogenetically oldest receptor tyrosine kinase: existence in the marine sponge Geodia cydonium.
Until now molecular data, elucidating the basis of invertebrate immunity are lacking. Previously both the gene and different cDNAs, coding for the ancestor of metazoan receptor tyrosine kinases (RTK), have been isolated from the marine sponge Geodia cydonium. The sponge RTK shows high polymorphism in the coding as well as in the non-coding parts of the gene. To further elucidate if the sponge RTK might be a molecule involved in self/non-self recognition the intracellular portion of the sponge RTK was expressed in Escherichia coli. The 59 kDa recombinant protein was used to raise monoclonal antibodies (McAb). The McAb recognized three polypeptides of sizes 135, 68 and 26 kDa by Western blotting. The McAb recognized only the plasma membranes of sponge cells as analyzed by immunohisto- and cytochemical studies. Northern blotting analysis revealed that the expression of the RTK gene depends on environmental conditions and on seasonal variations. Based on the high degree of polymorphism and on the immunochemical data we suggest that the RTK in G. cydonium might be involved in sponge immunity.
Skorokhod
A
A
Abteilung Angewandte Molekularbiologie, Universität of Mainz, Germany.
Schäcke
H
H
Diehl-Seifert
B
B
Steffen
R
R
Hofmeister
A
A
Müller
W E
WE
D000818:Animals; D019084:Fluorescent Antibody Technique, Indirect; D008565:Membrane Proteins / Q000378:metabolism; D008969:Molecular Sequence Data; D010802:Phylogeny; D011161:Porifera; D012333:RNA, Messenger / Q000378:metabolism*; D020794:Receptor Protein-Tyrosine Kinases / Q000235:genetics* / Q000378:metabolism; D015183:Restriction Mapping
D008565:Membrane Proteins; D012333:RNA, Messenger; D020794:Receptor Protein-Tyrosine Kinases