Open AccessPhosphorylation of STEF/Tiam2 by protein kinase A is critical for Rac1 activation and neurite outgrowth in dibutyryl cAMP–treated PC12D cells
Author(s) -
Akihiro Goto,
Mikio Hoshino,
Minoru Matsuda,
Takeshi Nakamura
Publication year - 2011
Publication title -
molecular biology of the cell
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.463
H-Index - 225
eISSN - 1939-4586
pISSN - 1059-1524
DOI - 10.1091/mbc.e10-09-0783
Subject(s) - neurite , rac1 , microbiology and biotechnology , biology , cdc42 , phosphorylation , growth cone , second messenger system , morphogenesis , axon guidance , protein kinase a , gtpase , axon , signal transduction , small gtpase , cyclin dependent kinase 5 , nerve growth factor , biochemistry , mitogen activated protein kinase kinase , receptor , in vitro , gene
The second messenger cAMP plays a pivotal role in neurite/axon growth and guidance, but its downstream pathways leading to the regulation of Rho GTPases, centrally implicated in neuronal morphogenesis, remain elusive. We examined spatiotemporal changes in Rac1 and Cdc42 activity and phosphatidylinositol 3,4,5-triphosphate (PIP 3 ) concentration in dibutyryl cAMP (dbcAMP)-treated PC12D cells using Förster resonance energy transfer–based biosensors. During a 30-min incubation with dbcAMP, Rac1 activity gradually increased throughout the cells and remained at its maximal level. There was no change in PIP 3 concentration. After a 5-h incubation with dbcAMP, Rac1 and Cdc42 were activated at the protruding tips of neurites without PIP 3 accumulation. dbcAMP-induced Rac1 activation was principally mediated by protein kinase A (PKA) and Sif- and Tiam1-like exchange factor (STEF)/Tiam2. STEF depletion drastically reduced dbcAMP-induced neurite outgrowth. PKA phosphorylates STEF at three residues (Thr-749, Ser-782, Ser-1562); Thr-749 phosphorylation was critical for dbcAMP-induced Rac1 activation and neurite extension. During dbcAMP-induced neurite outgrowth, PKA activation at the plasma membrane became localized to neurite tips; this localization may contribute to local Rac1 activation at the same neurite tips. Considering the critical role of Rac1 in neuronal morphogenesis, the PKA—STEF–Rac1 pathway may play a crucial role in cytoskeletal regulation during neurite/axon outgrowth and guidance, which depend on cAMP signals.