NGF activates the phosphorylation of MAP1B by GSK3β through the TrkA receptor and not the p75^NTRreceptor

Abstract

We have recently shown that nerve growth factor (NGF) induces the phosphorylation of the microtubule-associated protein 1B (MAP1B) by activating the serine/threonine kinase glycogen synthase kinase 3b (GSK3b) in a spatio-temporal pattern in PC12 cells that correlates tightly with neurite growth. PC12 cells express two types of membrane receptor for NGF: TrkA receptors and p75 NTR receptors, and it was not clear from our studies which receptor was responsible. We show here that brain-derived neurotrophic factor, which activates p75 NTR but not TrkA receptors, does not stimulate GSK3b phosphorylation of MAP1B in PC12 cells. Similarly, NGF fails to activate GSK3b phosphorylation of MAP1B in PC12 cells that lack TrkA receptors but express p75 NTR receptors (PC12 nnr). Chick ciliary ganglion neurons in culture lack TrkA receptors but express p75 NTR and also fail to show NGF-dependent GSK3b phosphorylation of MAP1B, whereas in rat superior cervical ganglion neurons in culture, NGF activation of TrkA receptors elicits GSK3b phosphorylation of MAP1B. Finally, inhibition of TrkA receptor tyrosine kinase activity in PC12 cells and superior cervical ganglion neurons with K252a potently and dose-dependently inhibits neurite elongation while concomitantly blocking GSK3b phosphorylation of MAP1B. These results suggest that the activation of GSK3b by NGF is mediated through the TrkA tyrosine kinase receptor and not through p75 NTR receptors. Keywords: glycogen synthase kinase 3b, microtubule-associated protein 1B, nerve growth factor, PC12 cells. Glycogen synthase kinase 3 (GSK3) is a highly conserved serine/threonine kinase, originally identified as a negative regulator of glycogen synthase, but more recently implicated in a wide range of signalling pathways, including ones influencing cell fate determination during embryogenesis and neuronal differentiation (Grimes and Jope 2001;Doble and Woodgett 2003). In vertebrates, there are two isoforms, GSK3a and GSK3b, encoded by separate genes (Woodgett 1990) and, although GSK3a is the dominant form in most tissues, GSK3b is particularly abundant in neural tissue (Woodgett 1990), where it is neuron-specific (Takahashi et al. 1994;Leroy and Brion 1999). In the CNS, GSK3b is developmentally regulated, with peak levels of expression during axonogenesis. It is present in growing axons but completely excluded from them at the end of axonogenesis, being restricted in the adult to neuronal cell bodies and dendrites (Leroy and Brion 1999). This suggests that GSK3b has a role in axonogenesis, an idea supported by pharmacological studies. GSK3 is inhibited by lithium ions (Klein and Melton 1996;Stambolic et al. 1996) and although other enzymes are also inhibited by lithium, in immature neurons, GSK3 appears to be the primary pharmacological target (Lucas et al. 1998;Hall et al. 2002; Owen and GordonWeeks 2003; but see Williams et al. 2002). Lithium has profound morphological effects on developing neurons in culture (Burstein et al. 1985;Hollander and Bennett 1991;Lucas and Salinas 19...

Nonprimed and DYRK1A-primed GSK3β-phosphorylation sites on MAP1B regulate microtubule dynamics in growing axons

“…This idea is consistent with the finding that MAP1B is downstream of various signalling pathways that stimulate neurite growth or direct growth-cone pathfinding, e.g. laminin (DiTella et al, 1996;Paglini et al, 1998), netrins (Del Rio et al, 2004), neurotrophins (Goold and Gordon-Weeks, 2001;Goold and Gordon-Weeks, 2003;Goold and Gordon-Weeks, 2005) and Wnts (Lucas et al, 1998;Ciani et al, 2004), or that influence neuronal migration, e.g. reelin (Gonzalez-Billault et al, 2005).…”

RASSF1A Interacts with Microtubule-Associated Proteins and Modulates Microtubule Dynamics

“…MAP1B is the earliest microtubule-associated protein expressed in the developing nervous system (18) and is thought to have roles on axonal transport and neurite outgrowth (19). More recently, MAP1B has been shown to be phosphorylated by glycogen synthase kinase-3␤ through the TrkA receptor and this correlates tightly with outgrowth of neuritis (20). Similar to RASSF1A, MAP1B is localized to microtubules and protects against depolymerization induced by nocodazole (21).…”

Kidins220/ARMS Modulates the Activity of Microtubule-regulating Proteins and Controls Neuronal Polarity and Development

“…This phosphorylation regulates MAP1b ability to maintain a more dynamically unstable microtubule population in the distal part of the axon when exposed to neurotrophin, netrin, and reelin (88,(93)(94)(95)(96). The rise in total MAP1b HC after Kidins220/ARMS knockdown could simply reflect an increase in axonal structural proteins to produce higher number of axons, and the phosphorylation decrease would promote axonal microtubule stabilization and outgrowth.…”