Membrane skeleton orchestrates the platelet glycoprotein (GP) Ib-IX complex clustering and signaling.

Dan Shang,Qian Wang,Tanner S Shaw,John N Van,Zuping Zhang,Yuandong Peng,Yali Ran

doi:10.1002/iub.1559

Abstract

SummaryPlatelet glycoprotein Ib‐IX complex is affixed to the membrane skeleton through interaction with actin binding protein 280 (ABP‐280). We find that removal of the ABP‐280 binding sites in GP Ibα cytoplasmic tail has little impact on the complex clustering induced by antibody crosslinking. However, large truncation of the GP Ibα cytoplasmic tail allows the formation of larger patches of the complex, suggesting that an ABP‐280 independent force may exist. Besides, we observe that the signaling upon GP Ib‐IX clustering is elicited in both membrane lipid domain dependent and independent manner, a choice that relies on how the membrane skeleton interacts with the complex. Our findings suggest a more complex mechanism for how the membrane skeleton regulates the GP Ib‐IX function. © 2016 The Authors IUBMB Life published by Wiley Periodicals, Inc. on behalf of International Union of Biochemistry and Molecular Biology, 68(10):823–829, 2016

Highlights

The GP Ib-IX complex is comprised of three type-I transmembrane polypeptides, GP Iba, GP Ibb and GP IX [1]
By utilizing K562, a human erythroleukemia cell line, we found that additional forces beyond the actin binding protein 280 (ABP-280)-mediated affixation may exist in regulating the clustering of the GP Ib-IX complex as well as in the signaling induced in these processes
Consistent with the previous finding that GP Iba evenly distributes on the platelet surface as detected by goldconjugated antibody staining [31], we found that the wild type cells showed uniform distribution of GP Iba on the cell surface (Fig. 1B, left column, c), whereas the control cells showed little sign of GP Iba-positive signals (Fig. 1B, left column, a), indicating that the labeling of GP Iba on these cells is specific

Summary

Introduction

The GP Ib-IX complex is comprised of three type-I transmembrane polypeptides, GP Iba, GP Ibb and GP IX [1]. Only GP Iba can associate with the membrane skeleton of both resting platelets and Chinese Hamster Ovary (CHO) cells through the interaction of its cytoplasmic tail (CT) with the actin binding protein (ABP-280) [3,4,5,6,7,8,9,10,11]. A number of investigations have suggested that GP Iba binding to ABP-280 facilitates resistance to high shear force upon vWf binding [12,13,14] and transmits signals for integrin activation [15,16]. Upon high shear induced vWf binding, platelets can form membrane tethers which originate from the initial discrete adhesion points (DAPs) and later develop multiple secondary DAPs. Abundant amounts of GP Iba was found on these DAPs [17,18]. Even though membrane tension can eventually be overcome, it does not occur until the hydrodynamic

Results

Discussion

Conclusion