Expression of apoptosis-associated speck-like protein containing a caspaserecruitment domain, a pyrin N-terminal homology domain-containing protein,in normal human tissues

Apoptosis-associated speck-like protein containing a caspase recruitment do main (ASC) is a pyrin N-terminal homology domain (PYD)- and caspase recruit ment domain (CARD)-containing a proapoptotic molecule. This molecule has al so been identified as a target of methylation-induced silencing (TMS)-1. We cloned the ASC cDNA by immunoscreening using an anti-ASC monoclonal antibo dy. In this study, we determined the binding site of the anti-ASC monoclona l antibody on ASC and analyzed the expression of ASC in normal human tissue s. ASC expression was observed in anterior horn cells of the spinal cord, t rophoblasts of the placental villi, tubule epithelium of the kidney, semini ferous tubules and Leydig cells of the testis, hepatocytes and interlobular bile ducts of the liver, squamous epithelial cells of the tons!] and skin, hair follicle, sebaceous and eccrine glands of the skin, and peripheral bl ood leukocytes. In the colon, ASC was detected in mature epithelia] cells f acing the luminal side rather than immature cells located deeper in the cry pts. These observations indicate that high levels of ASC are abundantly exp ressed in epithelial cells and leukocytes, which are involved in host defen se against external pathogens and in well-differentiated cells, the prolife ration of which is regulated.