Activation of Stress-Activated Protein Kinases Correlates with Neurite Outgrowth Induced by Protease Inhibition in PC12 Cells


  • Benoit I Giasson,

  • Wendy Bruening,

  • Heather D Durham,

  • Walter E Mushynski

  • The present address of Dr. B. I. Giasson is University of Pennsylvania School of Medicine, Philadelphia, PA 19104, U.S.A.

  • The present address of Dr. W. Bruening is Fox Chase Cancer Center, Philadelphia, PA 19111, U.S.A.

  • Abbreviations used : CI, N-acetyl-Leu-Leu-norleucinal ; ERK, extracellular signal-regulated kinase ; GST, glutathione S-transferase ; HSP, heat shock protein ; MAPK, mitogen-activated protein kinase ; MAP-KAPK-2/3, mitogen-activated protein kinase-activated protein kinase-2/3 ; MEK, mitogen-activated protein kinase/extracellular signal-regulated kinase kinase ; MG132, carbobenzoxy-Leu-Leu-leucinal ; NGF, nerve growth factor ; PAGE, polyacrylamide gel electrophoresis ; PI-3-kinase, phosphatidylinositol 3-kinase ; PSI, inhibitor of proteasomal chymotrypsin-like activity [carbobenzoxy-Ile-Glu-(O-tert-butyl)-Ala-Leu-aldehyde] ; RK, reactivating kinase ; SAPK, stress-activated protein kinase ; SDS, sodium dodecyl sulfate.

Address correspondence and reprint requests to Dr. W. E. Mushynski at Department of Biochemistry, McGill University, 3655 Drummond Street, Room 914, Montreal, Quebec, H3G 1Y6, Canada.


Abstract : PC12 cells are well characterized for their ability to differentiate into neuronal-like cells when challenged with nerve growth factor. It has been reported that the calpain and proteasome inhibitor N-acetyl-Leu-Leu-norleucinal (CI) is also able to induce neurite outgrowth in PC12 cells. In this study, we report that the inhibitor of proteasomal chymotrypsin-like activity, carbobenzoxy-Ile-Glu-(O-tert-butyl)-Ala-Leu-aldehyde (PSI), can also induce differentiation of PC12 cells. Induction of neurite outgrowth with PSI, CI, or its close analogue, carbobenzoxy-Leu-Leu-leucinal (MG132), was associated with stress-activated protein kinase (SAPK) activation. Neurite formation induced by protease inhibition was independent of mitogen-activated protein kinase/extracellular signal-regulated kinase, p38/reactivating kinase, or phosphatidylinositol 3-kinase activities. The exact mechanism by which protease inhibition activates SAPKs remains to be elucidated ; however, our results suggest that the SAPK signal transduction cascade may be an alternative and/or parallel pathway in the regulation of neuronal differentiation.