Abstract
Cell surface CD147 protein promotes production of matrix metalloproteinases and hyaluronan, associates with monocarboxylate transporters and integrins, and is involved in reproductive, neural, inflammatory, and tumor functions. Here we combined covalent cross-linking, mass spectrometric protein identification, and co-immunoprecipitation to show selective CD147 association with three major types of transporters (CD98 heavy chain (CD98hc)-L-type amino acid transporter, ASCT2, and monocarboxylate transporters) as well as a regulator of cell proliferation (epithelial cell adhesion molecule). In the assembly of these multicomponent complexes, CD147 and CD98hc play a central organizing role. RNA interference knock-down experiments established a strong connection between CD147 and CD98hc expression and a strong positive association of CD147 (and CD98hc) with cell proliferation. As the CD147-CD98hc complex and proliferation diminished, AMP-activated protein kinase (a cellular "fuel gauge") became activated, indicating a disturbance of cellular energy metabolism. Our data point to a CD147-CD98 cell surface supercomplex that plays a critical role in energy metabolism, likely by coordinating transport of lactate and amino acids. Furthermore we showed how covalent cross-linking, together with mass spectrometry, can be used to identify closely associated transmembrane proteins. This approach should also be applicable to many other types of transmembrane proteins besides those associated with CD98hc and CD147.
Highlights
Cell surface CD147 protein promotes production of matrix metalloproteinases and hyaluronan, associates with monocarboxylate transporters and integrins, and is involved in reproductive, neural, inflammatory, and tumor functions
Our data point to CD147 interacting with monocarboxylate transporters and with amino acid transporters (CD98 heavy chain (CD98hc)LAT1 and ASCT2) and a regulator of cell proliferation (EpCAM)
CD147 Protein Partners Identified by LC-MS/MS—FLAGtagged CD147 was expressed in HT1080 and MCF7 cells at levels only a little higher (1.4 –2.1-fold) than endogenous CD147
Summary
Cell surface CD147 protein promotes production of matrix metalloproteinases and hyaluronan, associates with monocarboxylate transporters and integrins, and is involved in reproductive, neural, inflammatory, and tumor functions. CD98hc immunoprecipitation yielded a large complex (170 –230 kDa) containing endogenous CD147 when covalent cross-linker (BS3) was added to HEK293 cells prior to Triton X-100 lysis (Fig. 4A, lane 9) but not when BS3 was omitted (lane 8).
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