JLK Isocoumarin Inhibitors: Selective - Secretase Inhibitors That Do Not Interfere With Notch Pathway In Vitro or In Vivo A. Petit, 1 A. Pasini, 2 C. Alves da Costa, 1 E. Ayral, 3 J.F. Hernandez, 3 C. Dumanchin-Njock, 1 C.J. Phiel, 4 P. Marambaud, 5 S. Wilk, 6 M. Farzan, 7 P. Fulcrand, 3 J. Martinez, 3 D. Andrau, 1 and F. Checler 1 * 1 Institut de Pharmacologie, Mole ´culaire et Cellulaire, CNRS, UMR6097, Valbonne, France 2 Division of Developmental Biology, National Institute for Medical Research, London, United Kingdom 3 LAPP, CNRS, UMR5810, Montpellier, France 4 Howard Hughes Medical Institute, University of Pennsylvania, Philadelphia 5 Department of Psychiatry, Mount Sinai School of Medicine, New York, New York 6 Department of Pharmacology, Mount Sinai School of Medicine, New York, New York 7 Harvard Medical School, Boston, Massachusetts -Secretase activity is involved in the generation of A and therefore likely contributes to the pathology of Alz- heimer’s disease. Blocking this activity was seen as a major therapeutic target to slow down or arrest A- related AD progression. This strategy seemed more doubtful when it was established that -secretase also targets other substrates including Notch, a particularly important transmembrane protein involved in vital func- tions, at both embryonic and adulthood stages. We have described previously new non-peptidic inhibitors able to selectively inhibit A cellular production in vitro without altering Notch pathway. We show here that in vivo, these inhibitors do not alter the Notch pathway responsible for somitogenesis in the zebrafish embryo. In addition, we document further the selectivity of JLK inhibitors by showing that, unlike other described -secretase inhibi- tors, these agents do not affect E-cadherin processing. Finally, we establish that JLKs do not inhibit -site APP cleaving enzymes (BACE) 1 and BACE2, -secretase, the proteasome, and GSK3 kinase. Altogether, JLK inhibi- tors are the sole agents to date that are able to prevent A production without triggering unwanted cleavages of other proteins. © 2003 Wiley-Liss, Inc. Key words: -secretase; inhibitors; amyloid  peptide; notch; NICD; presenilins; Alzheimer’s disease; process- ing; cadherins; proteasome; GSK3; BACE A peptides that accumulate as Alzheimer’s disease progresses are proteolytically derived from -amyloid pre- cursor protein (APP) by successive cleavages triggered by two enzyme(s) referred to as - and -secretases (Checler, 1995; Maury, 1995; Octave, 1995; Sisodia and Price, 1995; Thinakaran, 1999). The latter activity generates the C-terminus of A peptides, the nature of which deter- mines the biophysical properties of the amyloid peptides. Thus A42, which appears at early stages of the disease, is much more prone to aggregation (Burdick et al., 1992) than is its shorter 40 amino acid-long parent peptide, and it is thought to contribute to the initiation of the degen- eration process (Hardy and Higgins, 1992). It was there- fore reasonable to envision -secretase as a suitable ther- apeutic target. Presenilins 1 and 2 (PS1 and PS2) are two proteins that, when mutated, are responsible for most of familial forms of Alzheimer’s disease (Van Broeckhoven, 1995; Hardy, 1997; Checler, 1999; Tanzi and Bertram, 2001). It has been proposed that these proteins could participate to the formation of A and could even be the genuine, elusive -secretase (Wolfe, 2001a). Even if PS1 and 2 likely contribute to the -secretase pathway, their enzy- matic nature remains a matter of discussion (Checler, 2001; Wolfe, 2001a; Sisodia and St. George-Hyslop, 2002) and their absolute requirement for the -secretase process has been convincingly challenged. Endogenous secreted and intracellular A can be recovered from cells devoid of presenilins (Armogida et al., 2001; Wilson et al., 2002) indicating that there exists at least PS-dependent and PS-independent -secretase pathways. Overall, the nature of the -secretase awaits final demonstration. Contract grant sponsor: Aventis Pharma; Contract grant sponsor: INSERM; Contract grant sponsor: CNRS. A. Pasini’s current address is: LGPD, IBDM, Marseille, France. C. Dumanchin-Njock’s current address is: INSERM EMI 9906, Rouen, France. *Correspondence to: F. Checler, Institut de Pharmacologie, Mole ´culaire et Cellulaire, UMR6097 du CNRS, 660 route des Lucioles, Sophia- Antipolis, 06560 Valbonne, France. E-mail: checler@ipmc.cnrs.fr Received 7 March 2003; Revised 16 May 2003; Accepted 27 May 2003 Journal of Neuroscience Research 74:370 –377 (2003) © 2003 Wiley-Liss, Inc.