Nerve growth factor changes G protein levels and localization in PC12 cells

Abstract

Growth cones at the growing tips of developing neurites contain the machinery to transmit information from receptors to a variety of intracellular enzymes and ion channels. In order to understand how signals are transmitted across the membrane, we asked whether the multiplicity of signalling pathways in the growth cone is reflected by the diversity of G proteins found in this organelle. Our immunohistochemical analysis indicated that growth cones of differentiated PC12 cells contain at least 4 alpha G protein subunits, 3 that are pertussis toxin substrates (alpha o, alpha i-1, alpha i-2) and 1 that is not (alpha q). In addition to localization in the neurites and growth cones, alpha o, alpha i-1, alpha i-2, and alpha q were detected in intracellular perinuclear structures. We also analyzed the temporal change in G proteins in PC12 cells differentiated by treatment with nerve growth factor (NGF). Time course experiments have shown that alpha o and beta proteins coordinately increase after 2 days of treatment with NGF, reach a maximum at 4 days, and remain elevated. In contrast to alpha o, alpha i-2 reached a peak at 4 days, then declined to almost the basal level by day 7 of treatment with NGF. These data indicated that the levels of alpha o, alpha i-2, and beta are differentially regulated during NGF-induced neuronal differentiation in PC12 cells. The alpha o protein was highly concentrated at the tips of the growth cones before the cellular level of alpha o had increased appreciably, suggesting that the alpha subunits are translocated during the first stage of neurite development. In addition, not every neural process has the same high level of alpha o, suggesting that G proteins may help define the specialized functions of particular neurites within a single cell.

Regulation of Brain G-protein Go by Alzheimer's Disease Gene Presenilin-1

“…The distribution of G o␣ in Fig. 5 is consistent with previous studies (26,33). Similar results were obtained when we used anti-G o1 antibody (data not shown).…”

You Can’t Go Home Again: Transcriptionally Driven Alteration of Cell Signaling by NGF

“…It is highly expressed in brain and endocrine cells. It has been reported that levels of Gnao protein are elevated in NGF-treated PC12 cells (14)(15)(16) as well as concentrated in growth cones (16). Consistent with this, our SAGE analysis revealed a 10-fold induction of Gnao transcripts in response to NGF treatment.…”

Effect of deletion of the major brain G-protein ? subunit (?o) on coordination of G-protein subunits and on adenylyl cyclase activity

“…Many studies have described changes of ␣ and ␤␥ subunits, for example, in cellular differentiation (Watkins et al, 1987;Asano et al, 1989;Brabet et al, 1991;Zubiaur and Neer, 1993) and organ development (Milligan et al, 1987;Asano et al, 1988b;Luetje et al, 1988) or in response to hormones such as thyroid hormone (Ros et al, 1988;Rapiejko et al, 1989) and steroids (Chang and Bourne, 1987). However, these studies have not addressed the question that is the subject of the present study, namely whether or not their expression is coordinated such that the total levels of ␣ and ␤␥ subunits are equal to each other.…”