Regulation of progranulin expression and location by sortilin in oxygen–glucose deprivation/reoxygenation injury

Progranulin is a secreted glycoprotein expressed in neurons and microglial cells that is involved in maintaining physiological functions. Many studies have found that progranulin may play a protective role against ischemic brain injury, but little is known about how the expression level and cellular localization status of progranulin is regulated after hypoxia–ischemia. Research has confirmed that sortilin, encoded by SORT1, can bind with progranulin and deliver a mature secretory isoform of progranulin to lysosomes, and progranulin is then cleaved. In the present study, we aimed to figure out whether sortilin could affect the expression and cellular localization of progranulin and regulate cell apoptosis during hypoxia–ischemia. In this study, oxygen–glucose deprivation/reoxygenation (OGD/R) in primary cortical neurons was used to mimic hypoxic–ischemic episodes. After OGD/R, the neuroprotective effects of progranulin against hypoxia–ischemia were examined, and primary cortical neurons were transduced with a SORT1 knockdown lentivirus to inhibit the expression of sortilin. The results showed that sortilin inhibition increased PGRN expression and alleviated cell injury induced by hypoxia–ischemia. Additionally, sortilin inhibition was associated with less PGRN localization in lysosomes. All of these findings suggest that sortilin can regulate the expression of PGRN, most likely by transporting it to lysosomes and affecting the cell injury in hypoxia–ischemia.