HEK293T cells were untreated or treated with 50 μM GlcNAz with DMSO for 48 hr (control), or 7.5 nM BTZ alone for 48 hr (BTZ), or 10 nM BTZ for 48hr and 20 μM OSMI-1 for 24 hr (BTZ+OSMI-1). Cell lysis and Click chemistry-based purification were performed using Click-iT protein enrichment kit following to manufacturer’s protocols with some modifications. Proteins on the beads were digested by adding trypsin. The digests were desalted using GL-Tip SDB (GL Sciences), and the eluates were evaporated in a SpeedVac concentrator. LC-MS/MS analysis of the resultant peptides was performed on an EASY-nLC 1200 UHPLC connected to a Q Exactive Plus mass spectrometer through a nanoelectrospray ion source (Thermo Fisher Scientific). The peptides were separated on a 75 μm inner diameter × 150 mm C18 reversed phase column (Nikkyo Technos) with a linear gradient from 4–28% acetonitrile (ACN) for min 0–100 followed by an increase to 80% ACN during min 100–110. Dynamic exclusion was set to 10 sec. Raw data were analyzed directly against the SwissProt database restricted to Homo sapiens using Proteome Discoverer version 2.2