Analysis of a spatially regulated phosphotyrosine phosphatase identifies tyrosine phosphorylation as a key regulatory pathway in Dictyostelium.
We have cloned a Dictyostelium phosphotyrosine phosphatase (PTP1) with a catalytic domain showing approximately 38%-50% amino acid identity to those of other PTPs. PTP1 contains an approximately 99 amino acid insert and bacterially produced PTP1 possesses PTP activity. PTP1 is expressed at a very low level in vegetative cells, induced by 4 hr, and maximally expressed at the tight aggregate stage. PTP1-lacZ studies indicate that PTP1 is spatially localized to prestalk and anterior-like cell types. PTP1 gene disruptants show accelerated development, whereas strains overexpressing PTP1 to a high level fail to aggregate. Strains overexpressing moderate levels exhibit severe morphological defects following aggregation, including multiply tipped aggregates and morphologically aberrant fruiting bodies. Western blot analysis using anti-phosphotyrosine antibodies shows specific changes in the mutant strains when compared with wild-type cells. The results indicate that reversible protein-tyrosine phosphorylation and PTP1 play important regulatory roles during Dictyostelium development.
Howard
P K
PK
Department of Biology, University of California, San Diego, La Jolla 92093-0634.
Sefton
B M
BM
Firtel
R A
RA
D000595:Amino Acid Sequence; D000818:Animals; D015153:Blotting, Western; D002460:Cell Line; D003001:Cloning, Molecular; D004023:Dictyostelium / Q000201:enzymology* / Q000254:growth & development; D015971:Gene Expression Regulation, Enzymologic / Q000502:physiology*; D010766:Phosphorylation; D017027:Protein Tyrosine Phosphatases / Q000235:genetics* / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D014443:Tyrosine / Q000378:metabolism*
D011993:Recombinant Fusion Proteins; D014443:Tyrosine; D017027:Protein Tyrosine Phosphatases