CSM News
Electronic Edition
Volume 2, number 17
May 7, 1994

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==========
Abstracts
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REGULATION BY PROTEIN-TYROSINE PHOSPHATASE PTP2 IS DISTINCT FROM THAT
BY PTP1 DURING DICTYOSTELIUM GROWTH AND DEVELOPMENT

Peter K. Howard1,2, Marianne Gamper1, Tony Hunter2, and Richard A.
Firtel1,3

1Department of Biology Center for Molecular Genetics University of
California, San Diego 9500 Gilman Drive La Jolla, CA 92093-0634

and

2Molecular Biology and Virology Laboratory
The Salk Institute for Biological Studies
P.O. Box 85800
San Diego, CA 92186-5800

MOECLULAR AND CELLULAR BIOLOGY, in press.

ABSTRACT
    We have cloned a gene encoding a second Dictyostelium discoideum
(D. discoideum) protein-tyrosine phosphatase (PTP2) whose catalytic
domain has ~30-39% amino acid identity to those of other PTPs and a
41% amino acid identity to D. discoideum PTP1.  Like PTP1, PTP2 is a
non-receptor PTP with the catalytic domain located at the C- terminus
of the protein.  PTP2 has a predicted molecular weight of 43,000 and
possesses an acidic 58 amino acid insertion 24 amino acids from the
N-terminus of the conserved catalytic domain.  PTP2 transcripts are
expressed at moderate levels in vegetative cells and are induced
several-fold at the onset of development.  Studies with a PTP2-lacZ
reporter gene fusion indicate that PTP2, like PTP1, is preferentially
expressed in prestalk and anterior-like cell types during the
multicellular stages of development.  PTP2 gene disruptants (ptp2 null
cells) are not detectably altered in growth and show a temporal
pattern of development similar to that of wild-type cells.  ptp2 null
slugs and fruiting bodies, however, are significantly larger than
those of wild-type slugs, suggesting a role for PTP2 in regulating
multicellular structures.  D. discoideum strains overexpressing PTP2
from the PTP2 promoter exhibit growth rate and developmental
abnormalities, the severity of which corresponds to the level of PTP2
overexpression.  Strains with high overexpression of the PTP2 gene
grow slowly on bacterial lawns and produce small cells in axenic
medium.  When development is initiated in these strains, cells are
able to aggregate but then stop further morphogenesis for 6 to 8 h,
after which time a variable fraction of these aggregates continue with
normal timing, producing diminutive fruiting bodies.  These disruption
and overexpression phenotypes for PTP2 are distinct from the
corresponding mutant PTP1 phenotypes.  Immunoprobing PTP2 mutant
strains during growth and development with anti-phosphotyrosine
antibodies reveals several changes in the tyrosine phosphorylation of
proteins in PTP2 mutant strains compared with wild-type cells.  These
changes are different from those identified in the previously
characterized corresponding PTP1 disruption and overexpression mutant
strains.  Thus, although PTP2 and PTP1 are non-receptor PTPs with
similar spatial patterns of expression, our findings suggest that they
possess distinct regulatory functions in controlling D. discoideum
growth and development.

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[End CSM-News, volume 2, number 17]