Figure 4. Schematic overview of the post-translational processing of the VP-NP II gene product. Sequential modification of 164 amino-acid VP-NPII preprohormone in endoplasmic reticulum and golgi lead to trafficking through the regulated secretory pathway and ultimately release from neurosecretory vesicles in the posterior pituitary. VP-NPII precursor is complexed as tetramers or high oligomers during processing. A small amount of partially processed precursor is released through the constitutive secretory pathway. OT is processed in a similar manner.