In 38C B lymphocytes the membrane form of IgM is displayed on the cell surface whereas the secretory form of IgM is degraded. In the EH cell line, a light chain-deficient variant of 38C cells, the μ heavy chains are partially assembled with surrogate light chains characteristic of pre-B cells. In these cells neither the membrane (μm) nor the secretory (μs) forms of the μ heavy chain reach their final destination, and both are rapidly degraded. The degradation of μ chains in EH cells, like that of μs in 38C cells, is nonlysosomal and occurs prior to the trans-Golgi. However, while μs degradation in 38C cells is inhibited by brefeldin A, in EH cells μs and μm are retained and degraded by a brefeldin A-insensitive mechanism. These results indicate that degradation in EH cells occurs within the endoplasmic reticulum, whereas degradation in 38C cells requires exit from this compartment. Thus, μ heavy chains can be degraded in multiple sites along the secretory pathway. The location of the degradation process is determined by the developmentally regulated assembly species of the μ chains with either 'classical' or surrogate light chains.
|Number of pages||4|
|Journal||Journal of Biological Chemistry|
|State||Published - 1993|