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

前B细胞受体（pre-BCR）的表达在正常B细胞发育中必须受到严格的调控，其失调与B系细胞的异常（包括白血病发生）有关。然而，尽管目前提出了前BCR组分的转录沉默，但前BCR下调的潜在机制仍然难以捉摸。在这篇论文中，我们发现一种溶酶体膜蛋白Laptm 5通过自主的前BCR信号转导上调，然后通过促进其在溶酶体中的降解下调前BCR。值得注意的是，这一发现表明，通过调节Laptm 5，在蛋白质水平上存在另一种前BCR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.