cAMP promotes branching of laminin-induced neuronal processes.
Laminin is a potent stimulator of neurite outgrowth. We have examined the signal transduction events involved in the neuronal cell response to laminin. Cyclic nucleotides, calcium, and sodium-proton exchange do not appear to be required for the transduction of the laminin signal during neurite outgrowth. Direct measurement of cAMP and cGMP levels shows no changes in NG108-15 cells when cultured on laminin. Exogenous cAMP alone had no effect on either the rate of process formation or process length, but did alter the morphology of laminin-induced neurites. A four-fold increase in the number of branches per neurite and a two-to-three-fold increase in the number of neurites per cell were observed in both NG108-15 and PC12 cells cultured on laminin when either 8-BrcAMP or forskolin was added. The cAMP-induced branching was also observed when PC12 cells were cultured on a laminin-derived synthetic peptide (PA22-2), which contains the neurite-promoting amino acid sequence IKVAV. By immunofluorescence analysis with axonal or dendritic markers, the PC12 processes on laminin and PA22-2 were axonal, not dendritic, and the cAMP-induced morphological changes were due to axonal branching. These data demonstrate that changes in cAMP are not involved in laminin-mediated neurite outgrowth, but cAMP can modulate the effects of laminin.
Weeks
B S
BS
Laboratory of Developmental Biology, National Institute of Dental Research, National Institutes of Health, Bethesda, Maryland 20892.
Papadopoulos
V
V
Dym
M
M
Kleinman
H K
HK
D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology; D000262:Adenylyl Cyclases / Q000502:physiology; D000818:Animals; D002118:Calcium / Q000502:physiology; D002454:Cell Differentiation / Q000187:drug effects; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000494:pharmacology*; D006152:Cyclic GMP / Q000502:physiology; D005455:Fluorescent Antibody Technique; D066298:In Vitro Techniques; D007382:Intermediate Filaments / Q000378:metabolism; D007797:Laminin / Q000494:pharmacology*; D008565:Membrane Proteins / Q000378:metabolism; D009474:Neurons / Q000166:cytology*; D051381:Rats; D015398:Signal Transduction; D012964:Sodium / Q000502:physiology; D016708:Synaptophysin; D014407:Tumor Cells, Cultured
D007797:Laminin; D008565:Membrane Proteins; D016708:Synaptophysin; D005576:Colforsin; D015124:8-Bromo Cyclic Adenosine Monophosphate; D012964:Sodium; D000242:Cyclic AMP; D000262:Adenylyl Cyclases; D006152:Cyclic GMP; D002118:Calcium