Biosynthesis, processing and half-life of P-glycoprotein in a human multidrug-resistant KB cell

Akihiko Yoshimura, Yasuo Kuwazuru, Tomoyuki Sumizawa, Shun ichi Ikeda, Misako Ichikawa, Takashi Usagawa, Shin ichi Akiyama

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39 Citations (Scopus)


The biosynthesis, processing, and half-life of the drug efflux pump, P-glycoprotein, were studied in human multidrug-resistant KB (KB-C2) cells selected for resistance to colchicine. An antibody directed against a synthetic oligopeptide corresponding to the amino-acid sequence (Glu-393-Lys-408) of P-glycoprotein from human mdrl cDNA was prepared in rabbits. With immunoblotting and immunoprecipitation, we detected a 140-170 kDa protein in KB-C2 cells but not in parental sensitive KB cells. KB-C2 cells made a 125 kDa precursor that was slowly processed (t 1 2 = 45 min) to the mature form of 140-150 kDa. The processing rate of P-glycoprotein was slower than that of low-density lipoprotein receptor. We detected another 160-180 kDa smear band, which might be a completely denatured form of P-glycoprotein. With immunoblotting, a minor band of high molecular mass (greater than 500 kDa) was also detected and this form increased after the cells were treated with chemical cross-linker, 1,5-difluoro-2,4-dinitrobenzene. The half-life of P-glycoprotein was long; no significant loss of P-glycoprotein was observed within 24 h after synthesis. Cells treated with tumicamycin produced a 120 kDa from of P-glycoprotein which was no longer processed but showed stability similar to that of the mature 140-150 kDa form. Agents that reverse multidrug resistance, phorbol ester and transport substrate did not affect the stability of P-glycoprotein.

Original languageEnglish
Pages (from-to)307-314
Number of pages8
JournalBBA - General Subjects
Issue number3
Publication statusPublished - 1989 Sept 15
Externally publishedYes


  • (Human)
  • (KB cell)
  • Multidrug resistance
  • P-glycoprotein

ASJC Scopus subject areas

  • Biophysics
  • Biochemistry
  • Molecular Biology


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