Inner Surface Of Cell Membrane Research Articles

Conservation Law of Cell Bioelectricity Membrane Area and Ion Inequality Equation Based on Potassium Channel “Origami Windmill” Model

At present, there are misunderstandings and even subversive errors in the understanding of cellular bioelectricity phenomena. The theory explaining the mechanism of bioelectricity generation is the ionic theory, and the ionic theory is based on the membrane theory. The membrane theory may be the correct part, and the ionic theory does not give a definite affirmation; the membrane theory may be the wrong part, and ionic theory does not give a clear negative, instead, has been further strengthened in the later period. Whether it is membrane theory or ionic theory, the author has ignored the structure and characteristics of ion channels, and has not found the essence and law of ion exchange inside and outside the cell membrane. Therefore, the GHK equation and the H-H equation based on the ionic theory have congenital deficiencies. Therefore, it is necessary to put forward a new doctrine on this basis and establish a new mathematical model based on the new doctrine to re-explain the mechanism of bioelectricity generation scientifically and rationally. This paper is based on the principle of K+ channel “origami windmill” model, the conservation law of membrane area of cell action potential ion exchange was proposed, and establishes a new mathematical model of cell action potential based on the conservation law of membrane area—ion inequality equation. The expression of conservation law of membrane area: SA (t) + SB (t) = S0, the expression of the ion inequality equation: resting potential N = N0 + Vt; action potential N = N0+ 170t -90t2. The conservation law of membrane area holds that bioelectrical activity is a process in which different cations replace each other on the inner surface of the cell membrane. Cl- is already surrounded by the cell membrane at the beginning of cell membrane formation, which determines the “positive” and “negative” of the cell action potential; The cations such as Na+, K+, etc., the amount of mutual replacement on the inner surface of the cell membrane determines the amplitude of the action potential, and the ratio of mutual replacement complies with the principle that the membrane area is equal and the ions are not equal. The ion inequality equation, cited the kinematics principle, can not only reflect the nature and rule of cation exchange on the inner surface of cell membrane,but also can reasonable avoid cell membrane expansion force and ionic driving force, completed the bioelectricity generation mechanism from the qualitative to the quantitative expression, supports the preexistence of membrane theory, to verify the theory of brain cell activation, the theory of dove-likeparticles and “origami windmill” model, has opened up a scientific and quantitative description cell action potential new ways and means.

Roles of flotillins in tumors.

The identification and use of molecular biomarkers have greatly improved the diagnosis and treatment of malignant tumors. However, a much deeper understanding of oncogenic proteins is needed for the benefit to cancer patients. The lipid raft marker proteins, flotillin-1 and flotillin-2, were first found in goldfish retinal ganglion cells during axon regeneration. They have since been found in a variety of cells, mainly on the inner surface of cell membranes, and not only act as a skeleton to provide a platform for protein-protein interactions, but also are involved in signal transduction, nerve regeneration, endocytosis, and lymphocyte activation. Previous studies have shown that flotillins are closely associated with tumor development, invasion, and metastasis. In this article, we review the functions of flotillins in relevant cell processes, their underlying mechanisms of action in a variety of tumors, and their potential applications to tumor molecular diagnosis and targeted therapy.

Monolayers of a tetrazine-containing gemini amphiphile: Interplays with biomembrane lipids.

The property of a newly synthesized tetrazine derivative comprised of double C18-saturated hydrocarbon chain (C18-rTz-C18) has been studied in situ at the air-water interface. C18-rTz-C18 or a gemini amphiphile contributes to restriction of its tetrazine moiety on the interface, which is expected to be used for bioimaging and analytical reagents. Herein, to understand lateral interactions between Tz and biomembrane constituents, we investigated the interfacial behavior of Langmuir monolayers composed of C18-rTz-C18 and biomembrane lipids such as DPPC, DPPG, DPPE, PSM, and Cholesterol (Ch). The lateral interaction of the binary monolayers was analyzed with the surface pressure (π)-molecular area (A) and surface potential (ΔV)-A isotherms. These thermodynamic data indicate that all of the two-components are miscible with each other. In particular, as opposed to the others, the monolayer stability of DPPE, which is a major constituent of the inner surface of cell membranes, is attenuated by the small-amount addition of C18-rTz-C18. This specific interaction implies the membrane destruction from the inside. The phase behavior during monolayer compression was visualized with Brewster angle microscopy (BAM), fluorescence microscopy (FM), and atomic force microscopy (AFM). The obtained morphologies exhibit a coexistence state of two different liquid-condensed domains derived from extra phospholipids and phospholipids-C18-rTz-C18 monolayers.

Interactions of a Tetrazine Derivative with Biomembrane Constituents: A Langmuir Monolayer Study.

Tetrazine (Tz) is expected to be used for bioimaging and as an analytical reagent. It is known to react very fast with trans-cyclooctene under water in organic chemistry. Here, to understand the interaction between Tz and biomembrane constituents, we first investigated the interfacial behavior of a newly synthesized Tz derivative comprising a C18-saturated hydrocarbon chain (rTz-C18) using a Langmuir monolayer spread at the air-water interface. Surface pressure (π)-molecular area (A) and surface potential (ΔV)-A isotherms were measured for monolayers of rTz-C18 and biomembrane constituents such as dipalmitoylphosphatidylcholine (DPPC), dipalmitoylphosphatidylglycerol (DPPG), dipalmitoyl phosphatidylethanolamine (DPPE), palmitoyl sphingomyelin (PSM), and cholesterol (Ch). The lateral interaction between rTz-C18 and the lipids was thermodynamically elucidated from the excess Gibbs free energy of mixing and two-dimensional phase diagram. The binary monolayers except for the Ch system indicated high miscibility or affinity. In particular, rTz-C18 was found to interact more strongly with DPPE, which is a major constituent of the inner surface of cell membranes. The phase behavior and morphology upon monolayer compression were investigated by using Brewster angle microscopy (BAM), fluorescence microscopy (FM), and atomic force microscopy (AFM). The BAM and FM images of the DPPC/rTz-C18, DPPG/rTz-C18, and PSM/rTz-C18 systems exhibited a coexistence state of two different liquid-condensed domains derived mainly from monolayers of phospholipids and phospholipids-rTz-C18. From these morphological observations, it is worthy to note that rTz-C18 is possible to interact with a limited amount of the lipids except for DPPE.

Subcellular localization and dynamics of MysPDZ (Myo18A) in live mammalian cells

MysPDZ is an unconventional myosin belonging to the class XVIII myosin containing a KE (lysine and glutamine)-rich domain and a PDZ domain, which codistributes with actin fibers partially without any canonical actin binding sequence in its myosin head domain. Recently, we reported the identification of a novel isoform of MysPDZ lacking these domains and exhibiting subcellular localization and expression profile different from the original form of MysPDZ. In order to delineate domains directing the subcellular localization of MysPDZ, we performed co-immunoprecipitation experiments and image analyses using mutants of MysPDZ fused with enhanced yellow fluorescent protein. Co-immunoprecipitation analyses showed that MysPDZ can self-associate through its C-terminus coiled-coil domain and the KE-rich domain mediates the interaction with actin. We observed by image analyses that the codistribution with actin fibers and the localization in inner surface of cell membrane of MysPDZ are controlled by the KE-rich domain and the PDZ domain, respectively. Time lapse video microscopy showed that MysPDZ in the cytoplasm moves randomly and rapidly within short range and is allocated to a subcellular compartment without ATP hydrolysis by MysPDZ. This suggests that MysPDZ is a protein which is unlike most unconventional myosins. Our study uncovers a novel role of the KE-rich and PDZ domains in directing subcellular localization and also contributes to a better understanding of functional differences in MysPDZ isoforms.

Cell adhesion receptors and cancer

Cell-to-cell and cell-to-extracellular matrix (ECM) interactions in the functions of cell adhesion and signal transduction are important in global control of cell phenotypes and cell behavior and are crucial for maintenance of homeostasis and structural/functional stabilization of tissues and organs. Cell adhesion receptors are recognized as the molecular basis of cell adhesion. Cadherin and integrin are widely expressed adhesion receptors in most tissues. They are transmembrane glycoproteins which, through their cytoplasmic domain, bind to many proteins at the inner surface of cell membrane to form molecule-linkage complexes and then connect with the cytoskeleton. Through cell adhesion receptors a network functioning as cell adhesion and signal transduction is organized between tissue cells and cellECM. In this regard cell adhesion receptors play an important role in regulation of morphogenesis, cellcell recognition, cell migration, cell sorting and the determination of cell’s fate in development. They mediate cell functions and their fault expression is intimately correlated with development of disorders like cancer. Several isoforms of lntegrin were found to have tumor suppressor effect. Some components in the molecule-linkage of focal contact are actin-binding proteins as well as substrates of kinase in the lntegrin initiated signal pathway to play a role as signal transducer. Some of these molecules exhibited tumor suppressor effect too. Decreased expression of E-Cadherin has been demonstrated in many epithelium originated carcinomas. Cadherin associated membrane adhesion plaque molecule β-Catenin is also involved in the oncogene Wnt signal pathway. Both E-Cadherin and β-Catenin were proved respectively with tumor suppressor effect against invasiveness and metastasis. That Cadherin is important for the posttranslationally functional expression of Connexin has been supported by evidence from developmental biology and cancer cell differentiation studies to suggest that some sort of interrelation feedback control exists between the two signal pathways.

Ultrastructural Studies of Calcium Location during the “Catch” Contraction of Clam Smooth Adductor Muscle Cells

Contraction of molluscan adductors has been classified into three states; 1) resting state, 2) contracted state, 3) prolonged “catch” state. Among these, the “catch” state is considered a peculiar state, which requires little expenditure of energy, but in which contraction can be maintained for long periods. It is not yet known whether “catch” muscle contraction is regulated by Ca, or where Ca translocates during resting state through “catch” state, if the muscle contraction is regulated by Ca. We attempted to observe Ca translocation in muscle cells during contraction by the K-pyroantimonate method. We fixed “catch” muscle cells for electron microscopy with fixative including K-pyroantimonate, and observed where electron-dense precipitates, in which Ca is concentrated, were located in the muscle cells in the three states of contraction. At the resting state, precipitate was located at cell peripheries, in positions such as at the inner surface of cell membranes and in sarcoplasmic reticular systems (SRs). In the contracted state, they were located within the cytoplasm. At the “catch” state, they were found in both the cytoplasm and at peripheries, although the number of precipitates in peripheral areas was small. Thus, we show that calcium translocates in the cells during resting-contraction-catch cycles of “catch” muscle contraction.

Possible Role for Serine/Threonine Phosphorylation in the Regulation of the Heteroprotein Complex between the hsp90 Stress Protein and the pp60v-src Tyrosine Kinase

The abundant, cytoplasmic 90-kDa heat-shock protein associates transiently with the Rous sarcoma virus oncogenic protein tyrosine kinase, pp60v-src, directs its cellular trafficking and negatively regulates its kinase activity. Here we report that the serine/threonine phosphatase inhibitor, okadaic acid, destabilized the heat-shock protein 90-pp60v-src chaperone complex in v-src-transfected cells. Concomitant with complex destabilization by okadaic acid, phosphoserine was doubled and phosphothreonine was increased 20-fold in the heat-shock protein 90. Although phosphorylation of the total pool of immunoprecipitable pp60v-src was unchanged, okadaic acid slightly increased phosphoserine and phosphothreonine levels specifically in pp60v-src bound to heat-shock protein 90. The low level of tyrosine phosphorylation in the pp60v-src complexed with heat-shock protein 90 was further decreased by okadaic acid. Interestingly, okadaic acid-stabilized hyperphosphorylation of the heat-shock protein 90-pp60v-src complex lowered the level of pp60v-src in cell membranes, the functional location for pp60v-src. We suggest that serine/threonine phosphorylation of heat-shock protein 90 and/or pp60v-src functions as a regulatory molecular trigger to release pp60v-src from the chaperone complex at the inner surface of cell membranes.