Basolateral secretion of Wnt5a in polarized epithelial cells is required for apical lumen formation

Abstract

BSTRACTWnt5a regulates planar cell polarity in epithelial cells, but it remains to be determined whether Wnt5a and its receptors are sorted apically or basolaterally, and how Wnt5a signaling is involved in apical and basolateral polarization. We found that Wnt5a was secreted basolaterally in polarized kidney epithelial cells. The basolateral secretion of Wnt5a required Wntless (Wls), clathrin and adaptor protein 1 (AP-1). Wnt5a receptors were also localized to the basolateral membranes, but their sorting did not require Wls. Wnt5a-induced signaling was stimulated more efficiently at the basolateral side than the apical side of epithelial cells. Knockdown of Wnt5a delayed apical lumen formation of the epithelial cyst, and these phenotypes were rescued by wild-type Wnt5a, but not by a Wnt5a mutant that is secreted apically. Although apoptosis was not required for apical lumen formation in a wild-type cyst, apoptosis was necessary for eliminating luminal cells in a Wnt5a-depleted cyst. These results suggest that Wnt5a and its receptors are sorted to their correct destination by different mechanisms and that the basolateral secretion of Wnt5a is necessary for apical lumen formation in the epithelial cyst.

Deletion of Wnt5a in osteoclasts results in bone loss through decreased bone formation

“…WNT5A is a complex protein that not only has multiple isoforms, but that also undergoes many PTMs that dictate its cellular effects through interactions with different receptors . Our study validates and adds to the complexity of WNT5A by identifying a unique, posttranslational phosphorylated form of WNT5A that is produced and secreted exclusively by RANKL‐stimulated osteoclast precursors.…”

“…WNT5A was previously reported to undergo PTMs, which influence WNT5A secretion and affinity for frizzled receptors, as well as receptor‐specific internalization . We investigated whether osteoblast‐ and osteoclast‐produced WNT5A are modified by PTMs.…”

“…Our study validates and adds to the complexity of WNT5A by identifying a unique, posttranslational phosphorylated form of WNT5A that is produced and secreted exclusively by RANKL‐stimulated osteoclast precursors. While WNT5A is known to undergo extensive lipidation and glycosylation before secretion, reports of phosphorylation have not been described previously. This finding is also intriguing as it corresponds to the increase in Wnt5a gene and protein expression that occurs during osteoclastogenesis .…”

Wnt5a induces renal AQP2 expression by activating calcineurin signalling pathway

“…Previous reports showed that Wnt5a promotes apical membrane polarization by regulating Rac and Rho activities, leading to translocation of apical marker, such as F-actin, to apical region of MDCK or IEC6 cells3940. To examine whether apical membrane polarization affected AQP2 trafficking, we co-stained the mpkCCD cells with AQP2 and F-actin after the treatment with Wnt5a.…”

CKAP4 is a Dickkopf1 receptor and is involved in tumor progression

“…Recently, we demonstrated that different Wnts (Wnt3a, Wnt5a, and Wnt11) and Wnt receptors (frizzled 2, frizzled 7, LRP6, ROR2, and RYK) have distinct secretory and trafficking routes in polarized MDCK epithelial cells (30,31). For instance, Wnt3a was secreted basolaterally and LRP6 was trafHere we showed that CKAP4 is a receptor for DKK1 and DKK1/CKAP4 signaling promotes normal and cancer cell proliferation through the PI3K/AKT pathway.…”