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

Authors

  • 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

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.

Ancillary