Calreticulin is a multi-functioning protein located in the endoplasmic reticulum. Several functions have been attributed to calreticulin including lectin-like chaperoning, regulation of gene expression, cell adhesion, auto-immunity and calcium homeostasis. As an endoplasmic reticulum chaperone calreticulin regulates the maturation and folding of several trans-membrane proteins. We hypothesized that as an endoplasmic reticular protein it regulates the expression folding and maturation of epidermal growth factor receptor (EGFR). To date no information is available about the role of calreticulin in EGFR expression and folding.


Wild type calreticulin deficient (crt -/-) and mouse lung cancer cells isolated from transgenic mice over expressing calreticulin was used to examine the expression, localization and function of EGFR. Western blot analysis was used to determine the protein expression. Immunocytochemical staining of cells was utilized to determine localization of EGFR and AKT phosphorylation was used to determine changes in EGFR function.


Loss of calreticulin function resulted in a significant increase in the expression of EGFR as was determined by western blot analysis with anti-EGFR antibody. Similarly, lung tumor cell lines isolated from calreticulin over expressing cells expressed high levels of EGFR. Immunocytochemical staining of these cells did not show any significant change in the localization of EGFR in either calreticulin deficient or over expressing cells.

Our data also demonstrated an increase in the level of tyrosine phosphorylation in calreticulin deficient cells accompanied by a significant increase in the AKT phosphorylation in these cell lines suggesting an increase in EGFR activity.


Altered calreticulin expression does not affect EGFR receptor folding but rather increases its expression and function. Next we will examine whether changes in the EGFR is due to calreticulin's role as a regulator of intracellular calcium thus affecting transcription of EGFR (using quantitative RT-PCR technique).


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  1. A. Abraham, H.A. Ayash, H. Omar, H. Massaeli, N. Mesaeli, Enhanced EGFR expression and function in calreticulin deficient cells, QFARF Proceedings, 2010, BMPS4.
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