Proteomic analysis uncovers novel actions of the neurosecretory protein VGF in nociceptive processing.
Peripheral tissue injury is associated with changes in protein expression in sensory neurons that may contribute to abnormal nociceptive processing. We used cultured dorsal root ganglion (DRG) neurons as a model of axotomized neurons to investigate early changes in protein expression after nerve injury. Comparing protein levels immediately after DRG dissociation and 24 h later by proteomic differential expression analysis, we found a substantial increase in the levels of the neurotrophin-inducible protein VGF (nonacronymic), a putative neuropeptide precursor. In a rodent model of nerve injury, VGF levels were increased within 24 h in both injured and uninjured DRG neurons, and the increase persisted for at least 7 d. VGF was also upregulated 24 h after hindpaw inflammation. To determine whether peptides derived from proteolytic processing of VGF participate in nociceptive signaling, we examined the spinal effects of AQEE-30 and LQEQ-19, potential proteolytic products shown previously to be bioactive. Each peptide evoked dose-dependent thermal hyperalgesia that required activation of the mitogen-activated protein kinase p38. In addition, LQEQ-19 induced p38 phosphorylation in spinal microglia when injected intrathecally and in the BV-2 microglial cell line when applied in vitro. In summary, our results demonstrate rapid upregulation of VGF in sensory neurons after nerve injury and inflammation and activation of microglial p38 by VGF peptides. Therefore, VGF peptides released from sensory neurons may participate in activation of spinal microglia after peripheral tissue injury.
Departments of Neuroscience, Pharmaceutics, Pharmacology, and Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, Minnesota 55455, USA.
Maureen S
MS
Riedl
Patrick D
PD
Braun
Kelley F
KF
Kitto
Samuel A
SA
Roiko
Lorraine B
LB
Anderson
Christopher N
CN
Honda
Carolyn A
CA
Fairbanks
Lucy
L
Vulchanova
D000818:Animals; D001583:Benzoxazoles / Q000378:metabolism; D002478:Cells, Cultured; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005620:Freund's Adjuvant; D005727:Ganglia, Spinal / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D006930:Hyperalgesia / Q000139:chemically induced / Q000378:metabolism; D007093:Imidazoles / Q000494:pharmacology; D007249:Inflammation / Q000139:chemically induced / Q000378:metabolism; D008297:Male; D017628:Microglia / Q000187:drug effects / Q000378:metabolism; D009475:Neurons, Afferent / Q000378:metabolism; D009479:Neuropeptides / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology; D009619:Nociceptors / Q000502:physiology*; D009924:Organ Culture Techniques; D010147:Pain Measurement / Q000187:drug effects; D010455:Peptides / Q000494:pharmacology; D010523:Peripheral Nervous System Diseases / Q000209:etiology / Q000378:metabolism* / Q000473:pathology; D040901:Proteomics; D011725:Pyridines / Q000494:pharmacology; D011806:Quinolinium Compounds / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D011930:Reaction Time / Q000187:drug effects; D020917:Receptor, trkA / Q000378:metabolism; D018048:Receptors, Purinergic P2 / Q000378:metabolism; D058477:Receptors, Purinergic P2X3; D015398:Signal Transduction / Q000187:drug effects; D013119:Spinal Cord Injuries / Q000378:metabolism; D013997:Time Factors; D015854:Up-Regulation / Q000187:drug effects / Q000502:physiology
D001583:Benzoxazoles; D004791:Enzyme Inhibitors; D007093:Imidazoles; D009479:Neuropeptides; C546410:P2rx3 protein, rat; D010455:Peptides; D011725:Pyridines; D011806:Quinolinium Compounds; D018048:Receptors, Purinergic P2; D058477:Receptors, Purinergic P2X3; C522413:VGF peptide; C062040:Vgf protein, rat; C075296:1,1'-((4,4,7,7-tetramethyl)-4,7-diazaundecamethylene)bis-4-(3-methyl-2,3-dihydro(benzo-1,3-oxazole)-2-methylidene)quinolinium; D005620:Freund's Adjuvant; D020917:Receptor, trkA; C090942:4-(4-fluorophenyl)-2-(4-hydroxyphenyl)-5-(4-pyridyl)imidazole