A novel cGMP signalling pathway mediating myosin phosphorylation and chemotaxis in Dictyostelium.
Chemotactic stimulation of Dictyostelium cells results in a transient increase in cGMP levels, and transient phosphorylation of myosin II heavy and regulatory light chains. In Dictyostelium, two guanylyl cyclases and four candidate cGMP-binding proteins (GbpA- GbpD) are implicated in cGMP signalling. GbpA and GbpB are homologous proteins with a Zn2+-hydrolase domain. A double gbpA/gbpB gene disruption leads to a reduction of cGMP-phosphodiesterase activity and a 10-fold increase of basal and stimulated cGMP levels. Chemotaxis in gbpA(-)B(-) cells is associated with increased myosin II phosphorylation compared with wild-type cells; formation of lateral pseudopodia is suppressed resulting in enhanced chemotaxis. GbpC is homologous to GbpD, and contains Ras, MAPKKK and Ras-GEF domains. Inactivation of the gbp genes indicates that only GbpC harbours high affinity cGMP-binding activity. Myosin phosphorylation, assembly of myosin in the cytoskeleton as well as chemotaxis are severely impaired in mutants lacking GbpC and GbpD, or mutants lacking both guanylyl cyclases. Thus, a novel cGMP signalling cascade is critical for chemotaxis in Dictyostelium, and plays a major role in myosin II regulation during this process.
Bosgraaf
Leonard
L
Department of Biochemistry, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands.
Russcher
Henk
H
Smith
Janet L
JL
Wessels
Deborah
D
Soll
David R
DR
Van Haastert
Peter J M
PJ
D015105:3',5'-Cyclic-AMP Phosphodiesterases / Q000235:genetics / Q000378:metabolism; D000818:Animals; D002352:Carrier Proteins / Q000378:metabolism; D002633:Chemotaxis / Q000502:physiology; D006152:Cyclic GMP / Q000502:physiology*; D003599:Cytoskeleton / Q000378:metabolism; D004023:Dictyostelium / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D006162:Guanylate Cyclase / Q000235:genetics / Q000378:metabolism; D047908:Intracellular Signaling Peptides and Proteins; D024462:Myosin Type II / Q000378:metabolism*; D010766:Phosphorylation; D011499:Protein Processing, Post-Translational; D015800:Protozoan Proteins / Q000235:genetics / Q000378:metabolism*; D015290:Second Messenger Systems / Q000502:physiology*
D002352:Carrier Proteins; D047908:Intracellular Signaling Peptides and Proteins; D015800:Protozoan Proteins; C022994:cyclic GMP-binding protein; D015105:3',5'-Cyclic-AMP Phosphodiesterases; D024462:Myosin Type II; D006162:Guanylate Cyclase; D006152:Cyclic GMP