Generation and characterization of BAP-deficient cell lines

BAP29 and BAP31 are ubiquitously expressed integral membrane proteins of the ER. In B-lymphocytes, they transiently bind to the TM domains of mIgD and mIgM, both of which are BCR subunits. BAP29 and BAP31 are discussed to play a role in controlling ER export of certain TM proteins by an unknown mechanism. In particular, BAPs are considered candidates to mediate ER retention of mIg molecules in the absence of the BCR subunits Ig-alpha and Ig-beta. Evaluation of database sequence information led to the identification of BAP family members from animals, plants and fungi. BAP proteins are likely expressed in all eukaryotes and possess a characteristic composition of structural elements and sequence motifs. Similarities in protein sequence and locus architecture <br>suggest that mammalian BAP29 and BAP31 are paralogs that arose from a duplicated ancestral gene. To investigate the role of BAP proteins in the ER, mouse ES cells deficient for either BAP29, BAP31 or both were generated by a sequential gene targeting approach. Targeted disruption of the BAP31 locus was achieved using a novel type of targeting vector that combines conditional targeting with promoter trapping. BAP-deficient cells exhibit normal growth and morphology of secretory pathway membrane systems. ER retention of mIgs and their cell surface transport after BCR assembly was examined in wild-type and BAP-deficient ES cells transfected with GFP-mIg fusion proteins. BAP-deficient cells retain these fusion proteins in the ER and do not transport them to the cell surface unless Ig-alpha and Ig-beta are co-expressed. Thus, ER retention of mIgs and BCR assembly is not compromised in the absence of BAP29 and BAP31. The present study proposes a function of BAP proteins in ER quality control rather than export control. BAP29 and BAP31 may selectively recognize and remove misfolded TM domains to prevent spontaneous protein aggregation and loss of sorting control.

Author dc:creator

• Kuppig, Stephan

Contributors dc:contributor

• Reth, Michael

• BAP29
• BAP31
• Qualitätskontrolle
• Retention
• Knockout
• quality control

Repository record source_url

https://freidok.uni-freiburg.de/data/287

OAI identifier oai:identifier

oai:freidok.uni-freiburg.de:287