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. Author manuscript; available in PMC: 2013 Oct 1.
Published in final edited form as: Traffic. 2012 Jul 24;13(10):1307–1314. doi: 10.1111/j.1600-0854.2012.01395.x

Figure 2. Endocytic and secretory pathways in osteoblasts.

Figure 2

In addition to binding to PTH receptor (PTH1R), PTH has been recently shown to induce the endocytosis of TGF-β receptor II (TβRII) and PTH1R into early endosomes (EE), which attenuates the cognate signaling pathways of both receptors. OASIS is an endoplasmic reticulum (ER)-residing transcription factor of CREB/ATF family. It is truncated and translocated into the nucleus to promote type I collage expression in response to ER stress. Opt, osteopotentia, is a newly identified protein that regulates ER volume during osteoblast activation. Sec23, FGD1, and SCYL1BP1/Gorab in red color are proteins mutated in human genetic skeleton diseases. They regulate bone matrix secretion at ER and Golgi, respectively. RANKL, an osteoclast differentiation cytokine, is released from osteoblast secretory lysosomes (SL) regulated by Vps33 and Rab27.