Structural determinants involved in the regulation of CXCL14/BRAK expression by the 26 S proteasome.
The chemokine CXCL14/BRAK participates in immune surveillance by recruiting dendritic cells. CXCL14 gene expression is altered in a number of cancers, but protein expression levels have not been investigated. Here we report that CXCL14 protein can be expressed in primary epithelial cells; however, in several immortalized and cancer cell lines this protein is targeted for polyubiquitylation and proteasomal degradation. We determined the NMR structure of CXCL14 to identify motifs controlling its expression. CXCL14 adopts the canonical chemokine tertiary fold but contains a unique five amino acid insertion (41VSRYR45) relative to other CXC chemokines. Deletion or substitution of key residues within this insertion prevented proteasomal degradation. Furthermore, we defined a 15 amino acid fragment of CXCL14 that is sufficient to induce proteasomal degradation. This study elucidates a post-translational mechanism for the loss of CXCL14 in cancer and a novel mode of chemokine regulation.
Peterson
Francis C
FC
Department of Biochemistry, Medical College of Wisconsin, Milwaukee, WI 53226, USA.
Thorpe
Jeffery A
JA
Harder
Adam G
AG
Volkman
Brian F
BF
Schwarze
Steven R
SR
D000595:Amino Acid Sequence; D019743:Chemokines, CXC / Q000737:chemistry* / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D016209:Interleukin-8 / Q000737:chemistry; D008969:Molecular Sequence Data; D050505:Mutant Proteins / Q000378:metabolism; D019906:Nuclear Magnetic Resonance, Biomolecular; D046988:Proteasome Endopeptidase Complex / Q000737:chemistry / Q000378:metabolism*; D061988:Proteasome Inhibitors; D017433:Protein Structure, Secondary; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D013329:Structure-Activity Relationship; D014407:Tumor Cells, Cultured
C118056:CXCL14 protein, human; D019743:Chemokines, CXC; D004791:Enzyme Inhibitors; D016209:Interleukin-8; D050505:Mutant Proteins; D061988:Proteasome Inhibitors; D011993:Recombinant Fusion Proteins; D046988:Proteasome Endopeptidase Complex; C061553:ATP dependent 26S protease