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

Arman Javadi,George S Baillie,Emma Evergren,Mark GH Scott,Elodie Blondel-Tepaz,Ravi K Deevi,Frederick C Campbell

doi:10.7554/elife.24578

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 β-Arrestin1. Because β-Arrestin1 binds and suppresses the Cdc42 GTPase-activating protein ARHGAP21, we hypothesize that PTEN controls Cdc42 -dependent morphogenic processes through a β-Arrestin1-ARHGAP21 complex. Here, we show that PTEN knockdown (KD) impairs β-Arrestin1 membrane localization, β-Arrestin1-ARHGAP21 interactions, Cdc42 activation, mitotic spindle orientation and 3D glandular morphogenesis. Effects of PTEN deficiency were phenocopied by β-Arrestin1 KD or inhibition of β-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 β-Arrestin1, ARHGAP21 and Cdc42.

Highlights

PTEN is the second most commonly mutated tumor suppressor gene in human cancer (Cantley and Neel, 1999) and has a central role in multicellular morphogenesis (Martin-Belmonte et al, 2007; Jagan et al, 2013a; Deevi et al, 2016)
We found near-significant or significant differences of total lysate b-Arrestin1 and ARHGAP21 between PTEN-expressing and -deficient cells [Caco-2 vs ShPTEN (Figure 1A,B) and HCT116 vs PTEN -/- cells (Figure 1—figure supplements 1 and 2)]
Red and green fluorescence emitted by m-Cherry and Alexa 488 labels correspond to b-Arrestin1 and wheat germ agglutinin (WGA), respectively

Summary

Introduction

PTEN (phosphatase and tensin homolog) is the second most commonly mutated tumor suppressor gene in human cancer (Cantley and Neel, 1999) and has a central role in multicellular morphogenesis (Martin-Belmonte et al, 2007; Jagan et al, 2013a; Deevi et al, 2016). While PTEN antagonizes the phosphoinositol 3-kinase (PI3K)/AKT pathway via its N-terminal phosphatase domain (Cantley and Neel, 1999), three-dimensional (3D) multicellular assembly was unaffected by forced variation of PI3K activity in colorectal organotypic model systems (Jagan et al, 2013a; Magudia et al, 2012). Protein scaffolding enhances signaling efficiency by assembly of spatially distinct subcellular complexes for different cellular tasks (Weng et al, 1999; Pertz, 2010).

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Conclusion