https://www.cell.com/cell/pdf/0092-8674(92)90189-J.pdf

Sorting of GPI-anchored proteins to glycolipid-enriched membrane subdomains during transport to the apical cell surface

Solubilization of membranes by detergents

The cell biology of caveolae is a rapidly growing area of biomedical research. Caveolae are known primarily for their ability to transport molecules across endothelial cells, but modern cellular techniques have dramatically extended our view of caveolae. They form a unique endocytic and exocytic compartment at the surface of most cells and are capable of importing molecules and delivering them to specific locations within the cell, exporting molecules to extracellular space, and compartmentalizing a variety of signaling activities. They are not simply an endocytic device with a peculiar membrane shape but constitute an entire membrane system with multiple functions essential for the cell. Specific diseases attack this system: Pathogens have been identified that use it as a means of gaining entrance to the cell. Trying to understand the full range of functions of caveolae challenges our basic instincts about the cell.

The Caveolae Membrane System

The elucidation of the molecular architecture of cell membranes is a central goal for cell biology, as structure lies at the heart of function. The erythrocyte plasma membrane has long provided a favored testing ground for this inquiry. Human red blood cells are readily available, relatively homogeneous, and relevant to medicine. Their plasma membranes can be easily isolated intact and essentially free of contamination from other cells, organelles, and cytoplasmic contents. This membrane is complex enough to be interesting and, to some degree, representative, yet it is simple enough to be analyzed as a whole. These circumstances make it likely that the human red cell plasma membrane will be the first whose molecular anatomy is known in any degree of satisfying detail. The literature concerning the proteins of erythrocyte membranes and membranes in general has been the subject of repeated review (1 9). This article will focus on the localization and modes of association of individual major polypeptides within the human red cell membrane.

https://rupress.org/jcb/article-pdf/62/1/1/1386885/1.pdf

THE ORGANIZATION OF PROTEINS IN THE HUMAN RED BLOOD CELL MEMBRANE A Review

Lipid Rafts: Elusive or Illusive?

Treatment of isolated human erythrocyte membranes with Triton X-100 at ionic strength ⋍0.04 preferentially released all the glycerolipid and glycoprotein species. At low ionic strength, certain nonglycosylated polypeptides were also selectively solubilized. The liberated polypeptides were free of lipids, but some behaved as if associated into specific oligomeric complexes. Each detergent-insoluble ghost residue appeared by electron microscopy to be a filamentous reticulum with adherent lipoid sheets and vesicles. The residues contained most of the membrane sphingolipids and the nonglycosylated proteins. The polypeptide elution profile obtained with nonionic detergents is therefore nearly reciprocal to that previously seen with a variety of agents which perturb proteins. These data afford further evidence that the externally-oriented glycoproteins penetrate the membrane core where they are anchored hydrophobically, whereas the nonglycosylated polypeptides are, in general, bound by polar associations at the inner membrane surface. The filamentous meshwork of inner surface polypeptides may constitute a discrete, self-associated continuum which provides rather than derives structural support from the membrance.

Selective solubilization of proteins and phospholipids from red blood cell membranes by nonionic detergents

Publisher Summary This chapter reviews the recent electron microscopic and biochemical studies relevant to an understanding of the construction of myofibrils in striated muscle. Emphasis is placed on relating ultrastructural information to data obtained from the in vitro studies of the myofibrillar proteins and their respective myofilaments. It focuses primarily on vertebrate myofibrillogenesis, but as the problem is common to the development of all striated muscle, much of the discussion is relevant to both invertebrate and vertebrate species. It limits an analysis of the posttranslational steps in fibrillogenesis and the ultrastructural features of myogenic cells. The structure and chemistry of the organelle is reviewed briefly. The chapter presents data to indicate that the assembly of the free thick and thin myofilaments, into the double hexagonal array, can proceed in the absence of protein synthesis and may be another example of a self-assembly system. The distribution of polyribosomes in myogenic cells has been reviewed and it was concluded that no consistent morphological relationship exists between the polysome chains and the growing myofilaments. The close relationship of myofibrillogenesis to the inner surface of the plasma membrane has been noted and discussed at some length.

The synthesis and assembly of myofibrils in embryonic muscle.

The challenge presented by myofibril assembly in striated muscle is to understand the molecular mechanisms by which its protein components are arranged at each level of organization. Recent advances in the genetics and cell biology of muscle development have shown that in vivo assembly of the myofilaments requires a complex array of structural and associated proteins and that organization of whole sarcomeres occurs initially at the cell membrane. These studies have been complemented by in vitro analyses of the renaturation, polymerization, and three-dimensional structure of the purified proteins.

https://science.sciencemag.org/content/sci/251/4997/1039.full.pdf

Molecular Analysis of Protein Assembly in Muscle Development.

Dissociated myoblasts from 12-day chick embryos were cultured in monolayer, and the differentiation of skeletal muscle cells was studied by electron microscopy. The results have revealed a striking ultrastructural similarity between the in vivo and the in vitro developing muscle, particularly with respect to the myofibrils and sarcoplasmic reticulum. This study demonstrates that all the characteristic organelles of mature skeletal muscle can develop in vitro in the absence of nerves.

https://rupress.org/jcb/article-pdf/35/2/445/1384264/445.pdf

Donald A. Fischman

Papers

Selective solubilization of proteins and phospholipids from red blood cell membranes by nonionic detergents

The synthesis and assembly of myofibrils in embryonic muscle.

Molecular Analysis of Protein Assembly in Muscle Development.

The fine structure of embryonic chick skeletal muscle cells differentiated in vitro.

The in vitro cell fusion of embryonic chick muscle without DNA synthesis.