The Journal of Neuroscience, February 1, 2001, 21(3):865-874
A Novel Role for Protein Tyrosine Phosphatase SHP1 in Controlling
Glial Activation in the Normal and Injured Nervous System
Andrea
Horvat1,
Franz-Werner
Schwaiger1,
Gerhard
Hager1,
Frank
Bröcker1,
Robert
Streif1,
Pjotr G.
Knyazev2,
Axel
Ullrich2, and
Georg W.
Kreutzberg1
1 Department of Neuromorphology,
Max-Planck-Institute of Neurobiology and 2 Department of
Molecular Biology, Max-Planck-Institute of Biochemistry, D-82152
Martinsried, Germany
Tyrosine phosphorylation regulated by protein tyrosine kinases and
phosphatases plays an important role in the activation of glial cells.
Here we examined the expression of intracellular protein tyrosine
phosphatase SHP1 in the normal and injured adult rat and mouse CNS. Our
study showed that in the intact CNS, SHP1 was expressed in astrocytes
as well as in pyramidal cells in hippocampus and cortex. Axotomy of
peripheral nerves and direct cortical lesion led to a massive
upregulation of SHP1 in activated microglia and astrocytes, whereas the
neuronal expression of SHP1 was not affected. In vitro
experiments revealed that in astrocytes, SHP1 associates with epidermal
growth factor (EGF)-receptor, whereas in microglia, SHP1
associates with colony-stimulating factor (CSF)-1-receptor. In
postnatal and adult moth-eaten viable
(mev/mev) mice, which are
characterized by reduced SHP1 activity, a strong increase in reactive
astrocytes, defined by GFAP immunoreactivity, was observed throughout
the intact CNS, whereas neither the morphology nor the number of
microglial cells appeared modified. Absence of
3[H]-thymidine-labeled nuclei indicated that astrocytic
proliferation does not occur. In response to injury, cell number as
well as proliferation of microglia were reduced in
mev/mev mice, whereas the
posttraumatic astrocytic reaction did not differ from wild-type
littermates. The majority of activated microglia in mutant mice showed
rounded and ameboid morphology. However, the regeneration rate after
facial nerve injury in mev/mev
mice was similar to that in wild-type littermates. These results emphasize that SHP1 as a part of different signaling pathways plays an
important role in the global regulation of astrocytic and microglial
activation in the normal and injured CNS.
Key words:
tyrosine phosphorylation; signal transduction; protein
tyrosine phosphatase SHP1; peripheral nerve axotomy; facial nerve; hypoglossal nerve; sciatic nerve; direct cortical lesion; microglial
proliferation; mutant moth-eaten viable mice
Copyright © 2001 Society for Neuroscience 0270-6474/01/213865-10$05.00/0