The role for Laptm5 in the down-modulation of pre-B cell receptor

B细胞前受体（Pre-B cell receptor, pre-BCR）的表达在正常的B细胞发育过程中必须受到严格的调控，而其失调与B系细胞的异常有关，包括白血病的发生。然而，尽管目前提出了pre-BCR组分的转录沉默，但对pre-BCR下调的机制仍不明确。在本文中，我们发现溶酶体膜蛋白Laptm5通过自主bcr前信号上调，随后通过促进其在溶酶体中的降解下调bcr前信号。值得注意的是，这一发现表明，在蛋白质水平上，通过调控Laptm5，存在另一种bcr前下调机制。

Pre-B cell receptor (pre-BCR) expression has to be strictly regulated for normal B cell development, and its dysregulation is associated with anomalies of B-lineage cells, including leukemogenesis. However, it remained elusive on the mechanism underlying pre-BCR down-modulation although transcriptional silencing of pre-BCR component is currently proposed. In this paper, we found that a lysosomal membrane protein, Laptm5 is up-regulated via autonomous pre-BCR signaling, followed by pre-BCR down-modulation by promoting its degradation in lysosomes. Of note, this finding suggests there is another mechanism of pre-BCR down-modulation at the protein level through the regulation of Laptm5.