Spermatogenesis rescue in a mouse deficient for the ubiquitin ligase SCF^β-TrCP by single substrate depletion

Abstract

beta-TrCP, the substrate recognition subunit of a Skp1-Cul1-F-box (SCF) ubiquitin ligase, is ubiquitously expressed from two distinct paralogs, targeting many regulatory proteins for proteasomal degradation. We generated inducible beta-TrCP hypomorphic mice and found that they are surprisingly healthy, yet have a severe testicular defect. We show that the two beta-TrCP paralogs have a nonredundant role in spermatogenesis. The testicular defect is tightly associated with cell adhesion failure within the seminiferous tubules and is fully reversible upon beta-TrCP restoration. Remarkably, testicular depletion of a single beta-TrCP substrate, Snail1, rescued the adhesion defect and restored spermatogenesis. Our studies highlight an unexpected functional reserve of this central E3, as well as a bottleneck in a specific tissue: a single substrate whose stabilization is incompatible with testicular differentiation.

Regulation of the protein stability of EMT transcription factors

“…Interestingly, this phenotype is reversed upon Snail1 depletion. 89 These results suggest that b-TrCP1 and b-TrCP2 are redundant in controlling the stability of Snail1 and b-catenin, although, as happens for b-catenin, b-TrCP2 expression does not induce Snail1 degradation. 91 Therefore, more work is needed to understand whether the 2 homologues play an individual, synergistic, or redundant role in controlling Snail1 and b-catenin stability under different experimental conditions.…”

“…90 Similarly to b-catenin, Snail1 is stabilized upon the combined depletion of both ligases, obtained by expression of an sh-b-TrCP2 in b-TrCP1 knockout mice. 89 These double-deficient mice are normal although show a more severe testicular phenotype than the b-TrCP1(¡/¡) mice with absence of spermatids and meiotic cells. Interestingly, this phenotype is reversed upon Snail1 depletion.…”

“…88 This is consequence of the stabilization of the b-TrCP1 substrates cyclin A, cyclin B, and Emi1 but not b-catenin. 88,89 Curiously, at least in MEFs, b-catenin stabilization requires additional silencing of b-TrCP2 88 although this ubiquitin ligase does not interact with b-catenin. 90 Similarly to b-catenin, Snail1 is stabilized upon the combined depletion of both ligases, obtained by expression of an sh-b-TrCP2 in b-TrCP1 knockout mice.…”

Critical role for IL-1β in DNA damage-induced mucositis

“…gut immunity | anakinra | anti-IL-1 preventive therapy | cytotoxic side effects | graft-vs.-host disease O nly a few E3 ubiquitin ligases have been studied in vivo by gene disruption for the purpose of elucidating their functions and suitability as potential drug targets (1)(2)(3). Beta-transducin repeat containing protein (β-TrCP) is an E3 ubiquitin ligase that affects numerous major cell regulators (1,4,5), such as the effector of the Wnt pathway, β-catenin (6); the inhibitor of the NF-κB pathway, IκB (7); the cell cycle regulators CDC25A (8), WEE1 (9), Emi1 (10), and Bora (11); and DNA damage responsive proteins CDC25A and Claspin (12).…”

“…This redundancy may explain the mild phenotype observed upon in vivo ablation of β-TrCP1; the two best characterized substrates of β-TrCP, β-catenin and IκBα, do not accumulate in β-TrCP1-deficient MEFs (MEF β-TrCP1−/− ) (10). Furthermore, residual expression of ∼20% β-TrCP2 activity on a β-TrCP1-null background is sufficient for preserving homeostasis in most tissues (2). To gain a better understanding of in vivo β-TrCP functions, we created a floxed β-TrCP2 allele and crossed it to the β-TrCP1-null mouse (10).…”