G. Fenteany et Sl. Schreiber, SPECIFIC-INHIBITION OF THE CHYMOTRYPSIN-LIKE ACTIVITY OF THE PROTEASOME INDUCES A BIPOLAR MORPHOLOGY IN NEUROBLASTOMA-CELLS, Chemistry & biology, 3(11), 1996, pp. 905-912
Background: Lactacystin inhibits cell proliferation and induces a dist
inctive, predominantly bipolar (two-neurite-bearing) morphology in Neu
ro 2A murine neuroblastoma cells. It binds with high specificity to th
e multicatalytic 20S proteasome and inhibits at least three of its pep
tidase activities (chymotrypsinlike, trypsin-like and peptidylglutamyl
-peptide hydrolyzing), each at a different rate, without inhibiting ot
her known proteases. The chymotrypsin-like and trypsinlike activities
of the proteasome are inhibited most rapidly, and irreversibly. In an
effort to determine which of the peptidase activities needs to be inhi
bited for neurite outgrowth to occur, we treated Neuro 2A cells with p
eptide aldehydes that selectively inhibit different proteasome activit
ies. Results: Treatment with peptide aldehydes ending in a hydrophobic
residue, all of which inhibit the chymotrypsin-like activity, results
in a bipolar morphology in Neuro 2A cells, whereas treatment with a p
eptide aldehyde inhibitor of the trypsin-like activity does not lead t
o a detectable change in morphology. One of the inhibitors that induce
s neurite outgrowth has been previously shown to inhibit the chymotryp
sin-like activity of the proteasome without inhibiting the other appar
ently distinct peptidase activities that cleave after neutral residues
, the so-called 'branched chain amino acid preferring' (BrAAP) and 'sm
all neutral amino acid preferring' (SNAAP) activities, or the peptidyl
glutamyl-peptide hydrolyzing (PGPH) activity. Conclusions: The chymotr
ypsin-like activity appears to antagonize bipolar-type neurite outgrow
th in Neuro 2A cells, while the trypsin-like, PGPH, BrAAP and SNAAP ap
pear not to do so. Selective inhibition of a single peptidase activity
, as opposed to general inhibition of the proteasome, appears sufficie
nt to induce a specific cellular process. Selective inhibition might b
e useful in managing diseases where only one activity is involved with
out completely inhibiting the proteasome. It is also possible that end
ogenous regulators of the proteasome could affect cellular processes a
nd that certain peptidase activities of the proteasome may have roles
in specifying a given cell fate.