Neuronal thread
protein is a novel 21-kDa
protein that accumulates in brains with
Alzheimer's disease and exhibits developmentally associated changes in the level of expression. Recently, we discovered that primary human
primitive neuroectodermal tumor (
PNETs), malignant
astrocytomas, and several human
PNET and
glioblastoma cell lines also express thread
protein immunoreactivity. However, in addition to the 21-kDa species, there are approximately 17- and approximately 14-kDa thread
protein-immunoreactive molecules expressed in both
PNET and
glioblastoma cell lines and a fourth approximately 8-kDa thread
protein detected in
glioblastoma cell lines. Metabolic labeling studies demonstrated that the 21-kDa thread
proteins are phosphorylated, whereas the approximately 17-, approximately 14-, and approximately 8-kDa thread
proteins are not. Glycosylated residues were not detected in either the
PNET- or
glioblastoma-derived thread
proteins. Using a panel of
monoclonal antibodies, we observed differences between
PNET and
glioblastoma cells suggesting that the thread
proteins expressed in neuronal and glial cells are distinct. The levels of thread
protein immunoreactivity in both
PNET and glial cells were highest during the log phase of cell growth and lowest in serum-starved, nonproliferating cultures. The findings suggest that there are several distinct neuronal and glial derived thread
proteins expressed in the central nervous system and that their levels of expression may be modulated with cell growth.