ALL-TRANS RETINOIC ACID COMBINED WITH PHORBOL ESTER REGULATES CD300B EXPRESSION IN HUMAN MONOCYTIC THP-1 CELLS

Open Access
Author:
Wu, Yong
Graduate Program:
Nutrition
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
April 09, 2010
Committee Members:
  • A Catharine Ross, Thesis Advisor
Keywords:
  • retinoic acid
  • CD300B
  • THP-1 cells
Abstract:
Retinoic acid (RA), a bioactive retinoid, has long been recognized for its role in regulation of immune cell activities. CD300B, the newly-identified leukocyte cell surface receptor protein, was recently reported to trigger the immune response through its cell membrane adaptor protein in a human monocytic cell line, THP-1. Our previous microarray study showed that the mRNA expression of CD300B was significantly up-regulated by RA treatment. We hypothesize herein that RA, alone or with other cell activator such as phorbol ester PMA, regulates CD300B expression, both at the gene level and the protein level, in THP-1 cells. Our results showed that RA and PMA synergistically increased the expression of human CD300B mRNA. RA alone increased the level of human CD300B mRNA by 20-fold, while PMA alone increased CD300B mRNA by less than 5-fold. Interestingly, if we treated the THP-1 cells with RA and PMA at the same time, the combination increased the human CD300B mRNA level to about 60-fold, comparing to the control. Secondly, the expression of endogenous CD300B protein in THP-1 cells was increased by PMA treatment, but not RA treatment. Furthermore, CD300B molecules were mainly located on the plasma membrane and in the endosomal compartment, sharing a similar distribution pattern to transferrin receptor CD71. Finally, the cell signaling of PMA which induced the expression of CD300B mRNA was through the MEK/ERK pathway. Inhibition of MEK/ERK pathway abolished the CD300B induction by PMA, but not RA, indicating a different signaling pathway of expression regulation.