Interphase adhesion geometry is transmitted to an internal regulator for spindle orientation via caveolin-1.

Shigeru Matsumura,Seiichi Uchida,Fumiko Toyoshima,Akatsuki Kimura,Tokuko Haraguchi,Tomoko Kojidani,Yuji Kamioka

doi:10.1038/ncomms11858

Abstract

Despite theoretical and physical studies implying that cell-extracellular matrix adhesion geometry governs the orientation of the cell division axis, the molecular mechanisms that translate interphase adhesion geometry to the mitotic spindle orientation remain elusive. Here, we show that the cellular edge retraction during mitotic cell rounding correlates with the spindle axis. At the onset of mitotic cell rounding, caveolin-1 is targeted to the retracting cortical region at the proximal end of retraction fibres, where ganglioside GM1-enriched membrane domains with clusters of caveola-like structures are formed in an integrin and RhoA-dependent manner. Furthermore, Gαi1–LGN–NuMA, a well-known regulatory complex of spindle orientation, is targeted to the caveolin-1-enriched cortical region to guide the spindle axis towards the cellular edge retraction. We propose that retraction-induced cortical heterogeneity of caveolin-1 during mitotic cell rounding sets the spindle orientation in the context of adhesion geometry.

Highlights

Despite theoretical and physical studies implying that cell-extracellular matrix adhesion geometry governs the orientation of the cell division axis, the molecular mechanisms that translate interphase adhesion geometry to the mitotic spindle orientation remain elusive
To determine cellular dynamicity that correlates with the spindle orientation, we analysed the temporal transition of adhesive geometry from G2 phase to anaphase
The intercellular compartment of caveolin-1 vesicles was obviously detected in all cases, indicating that b1-integrin-dependent cell– extracellular matrix (ECM) adhesion is dispensable for the internalization of caveolin-1 during mitosis. These results demonstrate that, in cells cultured on an ECM, b1-integrin signals are a prerequisite for the localization of caveolin-1 within the cholesterol-enriched membrane microdomains (CEMMs) at the retracting cortical area during mitotic cell rounding and subsequently at the proximal end of the retraction fibres during metaphase

Summary

Introduction

Despite theoretical and physical studies implying that cell-extracellular matrix adhesion geometry governs the orientation of the cell division axis, the molecular mechanisms that translate interphase adhesion geometry to the mitotic spindle orientation remain elusive. Adhesion geometry has been shown to impose a force field on the cortex of metaphase cells through actin filament-based retraction fibres, which eventually dictates the spindle orientation[20] This spindle orientation requires the activity of Src kinase as well as Gai1–LGN–NuMA-mediated dynein-dependent pulling forces on the cortex, which are regulated by signals from centrosomes or chromosomes[17,21]. We show that RhoA-dependent mitotic cell rounding generates caveolin-1-associated cholesterol-enriched membrane microdomains (CEMMs) at the retracting cellular edges and subsequently at the proximal end of retraction fibres These domains are enriched with active RhoA, active b1-integrin and caveolin-1, and recruit the Gai1/LGN/NuMA complex to direct the spindle axis towards the cortex enriched with retraction fibres. Our findings provide the molecular basis that links interphase adhesion geometry with spindle orientation regulators

Methods

Results

Conclusion