USP32 is an active, membrane-bound ubiquitin protease overexpressed in breast cancers

Abstract

USP32, on chromosomal band 17q23.1-17q23.2, is a highly conserved but uncharacterized gene that gave rise during evolution to a well-known hominoid-specific proto-oncogene, USP6. We investigated the expression profile of USP32 in human tissues and examined its functions to gain insight into this novel member of the well-conserved ubiquitination system. We detected ubiquitous USP32 expression across tissues and confirmed the predicted deubiquitination function owing to the presence of conserved peptidase signature aspargine, cysteine, histidine, and aspartic acid domains of ubiquitin-specific proteases. A Golgi localization of GFP-fused USP32 was detected by fluorescent protection assay and BODIPY-TR staining. In addition, stable silencing of USP32 caused a significant decrease in the proliferation and migration rate of cells. Based on these and the fact that USP32 maps to 17q23, which is commonly amplified in breast cancers, we analyzed USP32 expression in breast cancer cells. We detected high expression of USP32 in 50% (9 of 18) of breast cancer cell lines and 22% (9 of 41) of primary breast tumors compared to mammary epithelial cells. In summary, we report the preliminary characterization of this novel deubiquitinating enzyme on 17q23 and demonstrate its functional role in the ubiquitin system and its potential involvement in tumorigenesis.

Mechanisms of regulation and diversification of deubiquitylating enzyme function

“…For example, farnesylation of UCH-L1 promotes its association with intracellular membranes and stimulates the accumulation of α-synuclein, which has been linked to Parkinson's disease, in neuroblastoma cells (Liu et al, 2009). The DUBs USP32, MINDY1 and MINDY2 (also known as FAM63A and FAM63B , respectively) are also predicted to be modified with lipids, which might account for the association of USP32 with intracellular membranes (Abdul Rehman et al, 2016;Akhavantabasi et al, 2010). Finally, reversible oxidation of the catalytic cysteine of DUBs, which inhibits their activity, has also been reported (Cotto-Rios et al, 2012;Kulathu et al, 2013;Lee et al, 2013); this could provide an attractive model for how ubiquitin signals can be amplified when DUB activity is reversibly inhibited in a spatio-temporal manner in response to production of reactive oxygen species.…”

miR-125b Targets ARID3B in Breast Cancer Cells

“…(sense: 5'-GATCCCCAGCTCCAGGCAGCAATTGATGTTCA-AGAGACATCAATTGCTGCCTGGAGCTTTTTTA-3' and antisense: 5'-AGCTTAAAAAAGCTCCAGGCAGCAATTGATGT-CTCTTGAACATCAATTGCTGCCTGGAGCTGGG-3'. Control oligos (sense: 5'-GATCCCCGTACGTTACGCGTAACGTATTC-AAGAGATACGTTACGCGTAACGTACTTTTTA-3' and antisense: 5'-AGCTTAAAAAGTACGTTACGCGTAACGTATCTC-TTGAATACGTTACGCGTAACGTACGGG-3') had no homology to human genome as was described previously (Akhavantabasi et al, 2010). Sequence confirmed constructs were transiently transfected to MCF7 cells by Fugene-HD (Roche) (3:2, Fugene: DNA ratio).…”

USP32 (ubiquitin specific peptidase 32)

“…Real-time PCR analysis in breast cancer cell lines determined that USP32 transcript is amplified more than two-fold in 50% of breast cancer cell lines and in 22% of (9 of 41) primary breast tumors compared to normal breast tissue samples. Moreover, silencing of USP32 leads to a decrease in the proliferation and migration properties of HeLa and MCF7 cells (Akhavantabasi et al, 2010). In estrogen receptor (ER) positive tumors, USP32 may have a higher copy number than ER negative tumors (Zhang et al, 2009).…”

“…Another study showed overexpression of USP32 in 50% (9 of 18) of breast cancer cell lines and 22% (9 of 41) of primary breast tumors compared to mammary epithelial cells (Akhavantabasi et al, 2010).…”

“…In addition, USP32 harbors Cys, His and Asp triad which is common in USP subfamily of DUBs (figure 3). Recently, active deubiquitination function of USP32 has been established (Akhavantabasi et al, 2010).…”