Extracellular HspBP1 inhibits formation of a cytotoxic Tag7-Hsp70 complex in vitro and in human serum

摘要

Tag7 (PGRP-S) was described as an innate immunity protein. Earlier we have shown that Tag7 forms with Hsp70 a stable complex with cytotoxic and antitumor activity. The same complex is formed in and secreted by cytotoxic T-lymphocytes. We have also found that Hsp-binding protein HspBPl incapacitates the Tag7-Hsp70 complex. Here we have studied the interaction of extracellular Tag7 and HspBPl. We have shown that HspBPl binds Tag7 in the conditioned medium of tumor CSMLO cells, thereby preventing formation of the cytotoxic Tag7-Hsp70 complex. We have also found that Tag7, if present in serum (in every third donor on average), is always in complex with HspBPl. This may be a protective measure against indiscriminate attack of the cytotoxic complex on normal cells.