Micro- and Nanoengineering of the Cell Surface

Jeffrey M Karp, Weian Zhao

• Publisher: William Andrew
• Year: 2014
• Print ISBN: 9781455731466
• eBook ISBN: 9781455731558
• Topic: Biological Sciences
• Subtopic: Cell Biology
• Index: Biological Sciences

Micro- and Nanoengineering of the Cell Surface explores the direct engineering of cell surfaces, enabling materials scientists and chemists to manipulate or augment cell functions and phenotypes. The book is accessible for readers across industry, academia, and in clinical settings in multiple disciplines, including materials science, engineering, chemistry, biology, and medicine. Written by leaders in the field, it covers numerous cell surface engineering methods along with their current and potential applications in cell therapy, tissue engineering, biosensing, and diagnosis. The interface of chemistry, materials science, and biology presents many opportunities for developing innovative tools to diagnose and treat various diseases. However, cell surface engineering using chemistry and materials science approaches is a new and diverse field. This book provides a full coverage of the subject, introducing the fundamentals of cell membrane biology before exploring the key application areas. - Demystifies the direct engineering of cell surfaces, enabling materials scientists and chemists to manipulate or augment cell functions and phenotypes - Provides a toolkit of micro- and nanoengineering approaches to the manipulation of the cell surface - Unlocks the potential of cell surface manipulation for a range of new applications in the fields of in vitro research, cell therapy, tissue engineering, biosensing, and diagnostics

Chapter 1

Cell Membrane Biology and Juxtacrine Signal Conversion

Mark L. Tykocinski, Department of Pathology, Anatomy and Cell Biology, Jefferson Medical College, Thomas Jefferson University, Philadelphia, PA, USA

Our contemporary view of the cell membrane pictures a highly dynamic structure endowed with a rich functional repertoire. This chapter describes the evolution of our understanding of membrane structure and function, and introduces the notion of ‘cell membrane emergence’ as a robust conceptual framework for bringing systems perspectives into this field. The notion of multi-tiered emergent states is of particular interest with respect to membrane proteins, in terms of their surface distribution, dynamic structure, and inbound and outbound signaling potential. Focusing on membrane protein-driven, intercellular ‘juxtacrine’ signaling, a scientific journey is showcased in which a succession of novel fusion protein paints and signal converter proteins have been developed for cell surface engineering and, in particular, juxtacrine signal conversion and rewiring of cellular networks.

Keywords

cell membrane biology; cell membrane emergence; juxtacrine communication; juxtacrine signal conversion; protein paints; signal converter proteins; auto-signaling; auto-apoptosis; auto-apoptosis; cell network modulation; cell surface protein interactome; autoimmune therapy; immunoregulation; cancer therapy

Outline

1.1 Introduction 1

1.2 Cell membrane biology—early milestones 2

1.3 Membrane microdomains 4

1.4 Cell membrane emergence 6

1.5 Juxtacrine signaling and rewiring cellular networks 8

1.6 Protein painting, artificial veto cell engineering 10

1.7 Trans signal conversion 11

1.8 Redirecting juxtacrine signals 14

1.9 Creating auto-signaling loops 15

1.10 SCP therapeutic flexibility 16

1.11 The cell membrane frontier 17

References 19

1.1 Introduction

The cell membrane, bulwark to the exterior and gateway to the interior, has emerged as a most remarkable biological structure. Complex in composition, organization, and biogenesis, it now reveals itself to be a dynamic, plastic, and functionally rich entity. As an ever more sophisticated experimental toolkit is deployed to probe the cell membrane’s complexities, our view of it is being enriched by the capacity to tease things apart—from single cell down to single molecule analytics—coupled to a growing ability to start to piece things back together again through system perspectives.

We are still a long way off from a “grand unification” that brings together the various perspectives and narratives of the biochemists, the biophysicists, the cellular physiologists, and the systems and computational biologists into a comprehensive, structurally, and functionally integrated view of the cell membrane. Cell surface proteomics, lipidomics, and glycomics are still in their infancy, and sophisticated tools to dissect and visualize static and dynamic macromolecular interplay are only now coming into play. Yet, though the cell membrane’s intricacies are yet to be unraveled, it has uncannily proven itself to be amenable to artificial manipulation. Quite remarkably, reductionism seems to work time and again, as simplistic interventions and modulatory inputs lead to predictable and utilitarian outputs. Somehow membrane engineering works despite the experimentalist’s indulgence in tunnel vision and conscious ignorance of the wider membrane biology panorama in its spatiotemporal complexity. Further, beyond the engineering of cell membranes, there are early successes in artificially mimicking them and recapitulating their functions in diverse and creative ways.

This chapter offers some historical highlights and perspectives on membrane biology, as a prelude to showcasing one early cell membrane engineering story line, directed toward the use of paintable and signal converter proteins to modulate cell membrane protein repertoires and their juxtacrine and autocrine signaling properties. Thinking about cell membranes is framed within a membrane emergence paradigm, with membrane engineering cast as a way to perturb and craft emergent cell membrane states for defined ends.

1.2 Cell Membrane Biology—Early Milestones

The history of cell membrane biology features a progression from simple lipid bilayer to complex macromolecular mixture, and from there to the current paradigm of a physiochemical entity that is intricate in substructure and dynamically molded by intrinsic and extrinsic factors. In the process, the cell membrane’s primitive “boundary” role, minimally tasked to envelop the cell’s constituents, has given way over time to a far richer constellation of functions, both outward and inward looking.

Our understanding of membrane biology has unfolded through several experimental narratives that have played out in parallel over the past century. Each narrative encompasses a series of historical milestones. These narratives are highly interwoven and relate to membrane composition and structure, membrane model systems, membrane protein structure and function, membrane biogenesis, and emergent properties of membranes.

A seminal insight into membrane composition and structure came in 1925, when Gorter and Grendel [1] proposed a lipid bilayer structure for cell membranes. This was built upon an interesting historical sequence of studies on the interaction of oil films with water, starting with Benjamin Franklin and furthered by Raleigh and then Langmuir [2]. The Gorter–Grendel lipid bilayer model was bolstered by a simple experimental observation: when lipids are extracted from erythrocytes, the area they cover at an air–water interface is twice as large as the original surface area of the cells. It became clear that the membrane bilayer results from the aggregation behavior of amphipathic phospholipids, in accordance with the hydrophobic effect, with the polar ends of the lipid molecules oriented toward the aqueous phase and the hydrophobic hydrocarbon regions organizing to prevent contact with the aqueous phase. The product is a planar biomolecular film separating two aqueous compartments. Proteins entered the picture in 1935 when Danielli and Davison offered a membrane model incorporating globular proteins [3]. Their image of a trilamellar sandwich, with globular proteins coating both surfaces of a lipid bilayer, was prompted by their attempt to accommodate the surface hydrophilicity of globular proteins. Their model was reinforced by the discovery back then of protein beta-sheet structure, which seemed to preclude protein penetration of the lipid bilayer. It was not until 1972 that the Danielli–Davison model was finally supplanted. In an alternative fluid mosaic model of cell membranes, Singer and Nicolson explicitly postulated two distinct classes of membrane proteins, peripheral and integral. Peripheral membrane proteins were defined as those removable with salt treatment or pH changes, whereas integral membrane proteins require detergents for removal, and importantly, can even span the entire membrane [4]. Various experimental findings had laid the groundwork for the Singer–Nicolson model, including the first high-resolution electron micrograph of a biological membrane by Palade [5], subsequently framed by Robertson into a “unit membrane” paradigm [6,7]; the elegant demonstration by Frye and Edidin [8], via experimental cell–cell fusion and fluorescein-labeled protein tracking, that membrane proteins can diffuse laterally in cell membranes; and the confirmation, by Hladky and Haydon [9], of the unit channel structure for Gramicidin A peptide.

Experiments with artificial membranes catalyzed this evolving understanding of membrane structure. A seminal milestone was the 1962 report by Mueller and Rudin [10] of the first artificial lipid bilayer. Such membrane modeling was taken to the functional level in 1969, when Huang [11] demonstrated that unilamellar lipid vesicles reconstituted with membrane proteins could be used to study ion flux. Since single membrane vesicles can be readily produced in large quantities, this technical achievement revolutionized transport studies, allowing insights into the kinetics of many channels, pumps, and transporters without having to know their structure. Next came the monolayer-derived planar bilayers of Montal and Mueller in 1972, virtually solvent-free synthetic membranes which allowed for the study of intrinsic properties of ion channels [12]. This technical advance set the stage for studying how lipid composition and distribution within cell membranes affects the activities of membrane proteins embedded in bilayers. In 1979, Schindler [13] described vesicle-supported planar bilayers, as synthetic membranes that are completely solvent free. The armamentarium of model membrane systems has continued to grow, including categories such as liposomes, sonicated vesicles, large unilamellar vesicles, black lipid membranes, lipid monolayers, high-density lipoprotein particles (reviewed in Ref. [14]), and dendrimersomes [15].

Another narrative that has in parallel shaped the membrane biology story revolves around membrane protein structure. Glycophorin was the first integral membrane protein to be sequenced, back in 1975 [16]. That same year, Henderson and Unwin [17] reported the first electron microscopy-derived structure for a membrane protein, bacteriorhodopsin. Its remarkable structure, with seven transmembrane α-helices, supported the notion that α-helices are the secondary structure of choice for transmembrane proteins. The first X-ray high-resolution structure of a membrane protein, by Diesenhofer, Huber and Michel in 1985, reinforced the image of an α-helical transmembrane segment [18]. The β-barrel model for bacterial porin and the β-helix structure of Gramicidin A, which came later, came to be seen as exceptions. Yet another landmark was the high-resolution structure of a bacterial ion channel, solved in 1999 by MacKinnon, which linked protein backbone structure, as opposed to the expected amino acid residues, to ion selectivity [19].

Then there are the functional narratives, diverse and multifaceted. Back in 1855, Naegeli and Cramer ascribed to plant cell membranes an essential role in osmosis. In the last decade of the nineteenth century, Ernest Overton [20] framed the theory that “lipoid” membranes enclosing animal and plant cells control their osmotic properties and permeation of molecules, and posited fundamental membrane processes such as ion transport. A multitude of signaling insights and milestones have ensued, along with breakthroughs touching on diverse membrane functions that extend well beyond signaling.

1.3 Membrane Microdomains

The notion that there may be spatial separation of signaling reactions within membranes was first proposed for the cAMP system in 1981 [21]. Early on, the Singer–Nicolson fluid mosaic model stood in the way of the idea that cells might spatially and functionally compartmentalize signaling machinery, with skepticism over whether laterally diffusible molecules could be segregated effectively. However, this compartmentalization concept, instantiated in the paradigm of membrane microdomains, has by now entered the mainstream, taking the fluid mosaic model in a different direction. While proteins move laterally within membranes, membrane surfaces are in fact nonhomogeneous, instead displaying heterogeneity in substructure, molecular distribution, and inner and outer connections. Thus the “fluid mosaic” can be recast as a “mosaic of microdomains” [22].

Membrane microdomains have been defined as functional regions, of micron/submicron dimensions, that compartmentalize proteins, lipids, and signaling components into multimolecular assemblies [23,24]. Over the years, microdomains have been categorized in different ways, with the delineation of lipid rafts, tetraspanin webs (TEMs), and caveolae (reviewed in Ref. [25]). Lipid rafts, with an estimated size of 12–200 nm, showcase bilayer asymmetry with outer leaflets composed of primarily cholesterol that binds to glycosphingolipids and inner leaflets composed of saturated phospholipids [26,27]. TEMs are a distin...

Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright
• Foreword
• List of Contributors
• Chapter 1. Cell Membrane Biology and Juxtacrine Signal Conversion
• Chapter 2. Cell Surface Engineering by Chemical Reaction and Remodeling
• Chapter 3. Bioconjugation Reactions in Living Cells: Development, Advances, and Applications of Glycan-Specific Technologies
• Chapter 4. Pushing the Bacterial Envelope: Strategies for Re-Engineering Bacterial Surfaces with Heterologous Proteins and Sugars
• Chapter 5. Noncovalent Functionalization of Cell Surface
• Chapter 6. Lipid-Mediated Cell Surface Engineering
• Chapter 7. Engineering the Surface of Cells Using Biotin–Avidin Chemistry
• Chapter 8. Construction and Computation with Nucleic Acids on the Cell Surface
• Chapter 9. Cell Surface Enzymatic Engineering-Based Approaches to Improve Cellular Therapies
• Chapter 10. Cell Microencapsulation for Tissue Engineering and Regenerative Medicine
• Chapter 11. Cell Engineering with Nanoparticles for Cell Imaging
• Chapter 12. Micro/Nano-Engineering of Cells for Delivery of Therapeutics
• Chapter 13. Molecular Engineering of Cell and Tissue Surfaces with Polymer Thin Films
• Chapter 14. Biofunctionalization of Hydrogels for Engineering the Cellular Microenvironment
• Chapter 15. Probe and Control of Cell–Cell Interactions Using Bioengineered Tools
• Index