Bone morphogenetic proteins (BMPs) are potent secreted signaling factors that trigger phosphorylation of Smad transcriptional regulators through receptor complex binding at the cell-surface. Resulting changes in target gene expression impact critical cellular responses during development and tissue homeostasis. BMP activity is tightly regulated in time and space by secreted modulators that control BMP extracellular distribution and availability for receptor binding. Such extracellular regulation is key for BMPs to function as morphogens and/or in the formation of morphogen activity gradients. Here, we review shuttling systems utilized to control the distribution of BMP ligands in tissue of various geometries, developing under different temporal constraints. We discuss the biological advantages for employing specific strategies for BMP shuttling and roles of varied ligand forms.

中文翻译：

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用于骨形态发生蛋白的微调穿梭机。

骨形态发生蛋白 (BMP) 是有效的分泌性信号因子，可通过细胞表面的受体复合物结合触发 Smad 转录调节因子的磷酸化。靶基因表达的结果变化会影响发育和组织稳态过程中的关键细胞反应。BMP 活性通过控制 BMP 细胞外分布和受体结合可用性的分泌调节剂在时间和空间上受到严格调节。这种细胞外调节是 BMP 作为形态发生素和/或形态发生素活性梯度形成的关键。在这里，我们回顾了用于控制不同几何形状组织中 BMP 配体分布的穿梭系统，在不同的时间约束下发展。