PTEN controls glandular morphogenesis through a juxtamembrane ß-Arrestin1/ARHGAP21 scaffolding complex.

ABSTRACT

PTEN controls three-dimensional (3D) glandular morphogenesis by coupling juxtamembrane signaling to mitotic spindle machinery. While molecular mechanisms remain unclear, PTEN interacts through its C2 membrane-binding domain with the scaffold protein ß-Arrestin1. Because ß-Arrestin1 binds and suppresses the Cdc42 GTPase-activating protein ARHGAP21, we hypothesize that PTEN controls Cdc42 -dependent morphogenic processes through a ß-Arrestin1-ARHGAP21 complex. Here, we show that PTEN knockdown (KD) impairs ß-Arrestin1 membrane localization, ß-Arrestin1-ARHGAP21 interactions, Cdc42 activation, mitotic spindle orientation and 3D glandular morphogenesis. Effects of PTEN deficiency were phenocopied by ß-Arrestin1 KD or inhibition of ß-Arrestin1-ARHGAP21 interactions. Conversely, silencing of ARHGAP21 enhanced Cdc42 activation and rescued aberrant morphogenic processes of PTEN-deficient cultures. Expression of the PTEN C2 domain mimicked effects of full-length PTEN but a membrane-binding defective mutant of the C2 domain abrogated these properties. Our results show that PTEN controls multicellular assembly through a membrane-associated regulatory protein complex composed of ß-Arrestin1, ARHGAP21 and Cdc42.