Deubiquitylation Machinery Is Required for Embryonic Polarity in Caenorhabditis elegans

Abstract

The Caenorhabditis elegans one-cell embryo polarizes in response to a cue from the paternally donated centrosome and asymmetrically segregates cell fate determinants that direct the developmental program of the worm. We have found that genes encoding putative deubiquitylating enzymes (DUBs) are required for polarization of one-cell embryos. Maternal loss of the proteins MATH-33 and USP-47 leads to variable inability to correctly establish and maintain asymmetry as defined by posterior and anterior polarity proteins PAR-2 and PAR-3. The first observable defect is variable positioning of the centrosome with respect to the cell cortex and the male pronucleus. The severity of the polarity defects correlates with distance of the centrosome from the cortex. Furthermore, polarity defects can be bypassed by mutations that bring the centrosome in close proximity to the cortex. In addition we find that polarity and centrosome positioning defects can be suppressed by compromising protein turnover. We propose that the DUB activity of MATH-33 and USP-47 stabilizes one or more proteins required for association of the centrosome with the cortex. Because these DUBs are homologous to two members of a group of DUBs that act in fission yeast polarity, we tested additional members of that family and found that another C. elegans DUB gene, usp-46, also contributes to polarity. Our finding that deubiquitylating enzymes required for polarity in Schizosaccharomyces pombe are also required in C. elegans raises the possibility that these DUBs act through an evolutionarily conserved mechanism to control cell polarity.

A Degenerate Cohort of Yeast Membrane Trafficking DUBs Mediates Cell Polarity and Survival*

“…Surprisingly, while multiple Ub'n enzymes (E1, E2, and E3) are essential in yeast (6 -8), only a single DUB is essential for viability of both budding and fission yeasts (6 -11), suggesting that considerable functional overlap may exist in yeast under standard laboratory conditions. In contrast, in metazoans, knockdown or loss of individual DUBs often results in developmental defects or disease states (3,12,13). Consistent with this possibility, we previously found that loss of five DUBs (5DUB delete: ubp4⌬1 ubp5⌬ ubp9⌬ ubp15⌬ sst2⌬) but not any combination of four intracellular membrane trafficking DUBs significantly impacted cell polarity, Ub conjugate accumulation, and viability in S. pombe (1).…”

The Deubiquitylase MATH-33 Controls DAF-16 Stability and Function in Metabolism and Longevity

“…The effect of math-33 inactivation on the Psod-3::GFP reporter activity was further analyzed using the math-33(tm3561) allele, which has been previously characterized as a loss-of-function allele in the context of early embryonic polarity establishment (McCloskey and Kemphues, 2012). In our experiments, math-33 inactivation by the loss-of-function math-33(tm3561) allele in daf-2(e1370) nematodes reduced Psod-3::GFP reporter activity to a level similar to that observed in daf-16(mu86); daf-2(e1370) control animals (Figure 2A).…”

The WD40-repeat Proteins WDR-20 and WDR-48 Bind and Activate the Deubiquitinating Enzyme USP-46 to Promote the Abundance of the Glutamate Receptor GLR-1 in the Ventral Nerve Cord of Caenorhabditis elegans

“…Consistent with this idea, USP-46 and its homologs have been shown to function together with other DUBs in several systems. USP-46 functions together with USP-47 and MATH-33/USP7 to regulate cell polarity in the C. elegans embryo (26), and the USP46 homolog Ubp9 functions redundantly with several other DUBs to regulate endocytosis and cell polarity in S. pombe (24) and mitochondrial function in S. cerevisiae (23). Further genetic and biochemical analysis will be required to identify the usp-46-independent mechanisms by which the WDR proteins regulate GLR-1.…”

“…USP-46 and its homologs have been implicated in regulating diverse cellular functions, including endocytosis, cell polarity, signal transduction, chromatin modification, and mitochon-drial biogenesis (22)(23)(24)(25)(26)(27). In some cases, the substrates of the DUB have been identified.…”