Characterization of two plasma membrane proteins abundant in rat brain

The Journal of Cell Biology

1990

Section: Resultssupporting

confidence: 81%

Section: Resultsmentioning

confidence: 56%

mentioning

confidence: 84%

See 1 more Smart Citation

Regulation of immunoreactive GAP-43 expression in rat cortical macroglia is cell type specific.

Cunha

The Journal of Cell Biology

1990

“…Molecular parameters, tissue localization, reactivity with anti-GAP-43 antibody, and phosphorylation by PKC, indicated that this protein was GAP-43 (1). A polypeptide with the same molecular parameters as GAP-43 appeared to be present in astrocytic plasma membranes as well (1). To increase the resolution of acidic proteins and the accuracy of determining their pI values, we altered the pH gradient in IEF gels from pH 4.2-8.5 to about pH 2.0-5.5.…”

Section: Resultsmentioning

confidence: 99%

“…We have described two brain-specific plasma membrane proteins that are very abundant in rat cortex (1). The smaller polypeptide was identified as growth-associated protein 43 (GAP-43) because of its relative molecular mass (=43 kDa), pI value (pI 4.3), in vitro phosphorylation by protein kinase C (PKC), and reactivity with anti-GAP-43 antibody.…”

mentioning

confidence: 99%

The 43-kDa neuronal growth-associated protein (GAP-43) is present in plasma membranes of rat astrocytes.

Proc. Natl. Acad. Sci. U.S.A.

Steisslinger

Aloyo

et al. 1988

One of the neuronal growth-associated proteins, GAP-43 (molecular mass, -43 kDa; pI 4.3), is abundant in growth-cone membranes and corresponds to a major protein kinase C substrate, the 46-kDa phosphoproteiw (pp46), of a growth-cone-enriched subcellular fraction. This protein has the following additional designations (depending on context): B-50 (phospholipid metabolism), F1 (synaptic plasticity), and p57 (calmodulin binding). We show that a protein with the same molecular mass and isoelectric point as GAP-43, which interacts with anti-GAP-43 antibodies on immunoblots, is present in the plasma membranes of cultured neonatal rat cortical astrocytes. Double-immunofluorescence labeling of cells with a serum against glial fibrillary acidic protein and anti-GAP-43 antibody was observed. Furthermore, astrocytic protein was phosphorylated in vitro by protein kinase C and comigrated in two-dimensional PAGE with GAP-43. The data indicate that GAP-43, heretofore believed to be neuronspecific, is present in at least one class of glial cells.Astrocytes constitute about one-half of all glial cells in the central nervous system. Although their precise functions are unknown, data indicate that they may be involved in a symbiotic relationship with neurons and thereby play important roles in neuronal development and function. This suggests that a significant aspect of astrocytic activity involves its plasma membrane. However, astrocytic plasma membranes remain to a large extent biochemically uncharacterized and, as such, their capacity for interacting with their environment is unknown. In this report, the proteins of the astrocytic plasma membrane are characterized by twodimensional PAGE, immunoblotting, and comparison with membranes from other cell types.We have described two brain-specific plasma membrane proteins that are very abundant in rat cortex (1). The smaller polypeptide was identified as growth-associated protein 43 (GAP-43) because of its relative molecular mass (=43 kDa), pI value (pI 4.3), in vitro phosphorylation by protein kinase C (PKC), and reactivity with anti-GAP-43 antibody. A polypeptide with these characteristics has been identified by several groups and designated F1, B-50, and a 46-kDa phosphoprotein (pp46) (2). Since this protein is developmentally regulated and its synthesis increases in regenerating axons, it was named growth-associated protein 43 (3). We show here that a protein with a molecular mass and a pI value similar to those of neuronal GAP-43 is present in the plasma membranes of cultured rat astrocytes. Two anti-GAP-43 antibodies interacted with this protein on immunoblots and mediated fluorescent labeling of cultured astrocytes. It is currently believed that GAP-43 is exclusively a neuronal protein. The presence of GAP-43 in astrocytic membranes may have important implications for the role of this protein in nervous system development.

Growth-associated protein 43 is down-regulated in cultured astrocytes

Mersel

1989

Metab Brain Dis

Growth-associated protein 43 (GAP-43: other designations--pp46, F1, B-50, p-57) is an abundant, neural, membrane-associated protein involved in synaptic plasticity and regeneration. We recently reported that GAP-43 is present in plasma membranes of cultured rat astrocytes. In the present study the level of astrocytic GAP-43 was assessed by indirect immunofluorescence labeling of cells with a specific anti-GAP-43 serum and immunoblotting of plasma membrane proteins. The results indicate that all astrocytes from 1-day-old cortex contained GAP-43 and those differentiated in culture did not. Furthermore, GAP-43 decreased dramatically during 3 weeks in culture. These results are consistent with the developmental down-regulation of GAP-43 in vivo.