Substrate recognition component of both SCF (SKP1-CUL1-F-box protein) and DCX (DDB1-CUL4-X-box) E3 ubiquitin-protein ligase complexes. Substrate recognition component of the SCF(FBXW5) E3 ubiquitin-protein ligase complex which mediates the ubiquitination and subsequent proteasomal degradation of SASS6 during S phase, leading to prevent centriole reduplication. The SCF(FBXW5) complex also mediates ubiquitination and degradation of actin-regulator EPS8 during G2 phase, leading to the transient degradation of EPS8 and subsequent cell shape changes required to allow mitotic progression. Substrate-specific adapter of the DCX(FBXW5) E3 ubiquitin-protein ligase complex which mediates the polyubiquitination and subsequent degradation of TSC2. May also act as a negative regulator of MAP3K7/TAK1 signaling in the interleukin-1B (IL1B) signaling pathway. Protein modification; protein ubiquitination. Part of the SCF (SKP1-CUL1-F-box) E3 ubiquitin-protein ligase complex SCF(FBXW5) composed of CUL1, SKP1, RBX1 and FBXW5. Component of the DCX(FBXW5) E3 ubiquitin ligase complex, at least composed of (CUL4A or CUL4B), DDB1, FBXW5 and RBX1. Interacts with CDC20, EPS8, TSC1, TSC2 and SASS6. Interacts with TNFAIP8L1; TNFAIP8L1 competes with TSC2 to bind FBXW5 increasing TSC2 stability by preventing its ubiquitination. Degraded by the APC/C complex during G1 phase and reaccumulates at the G1/S phase transition. The F-box domain mediates interaction with components of SCF (SKP1-CUL1-F-box protein) complexes, while WD repeats mediate interaction with components of DCX (DDB1-CUL4-X-box) complexes. The D-box (destruction box) mediate the interaction with APC proteins, and acts as a recognition signal for degradation via the ubiquitin-proteasome pathway. Phosphorylated at Ser-151 by PLK4 during the G1/S transition, leading to inhibit its ability to ubiquitinate SASS6. Ubiquitinated and degraded by the APC/C complex during mitosis and G1 phase. Belongs to the FBXW5 family. Truncated N-terminus.