Capsaicin, the main pungent ingredient in 'hot' chilli peppers, elicits a sensation of burning pain by selectively activating sensory neurons that convey information about noxious stimuli to the central nervous system We have used an expression cloning strategy based on calcium influx to isolate a functional cDNA encoding a capsaicin receptor from sensory neurons This receptor is a non-selective cation channel that is structurally related to members of the TRP family of ion channels The cloned capsaicin receptor is also activated by increases in temperature in the noxious range, suggesting that it functions as a transducer of painful thermal stimuli in vivo

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The capsaicin receptor: a heat-activated ion channel in the pain pathway

Effector functions in the immune system are carried out by a variety of cell types, and as our understanding of the complexity of the system expands, the number of recognized subdivisions of cell types also continues to increase. B lymphocytes, producing antibody, were initially distinguished from T lymphocytes, which provide help for B cells (1, 2). The T-cell population was further divided when surface markers allowed separation of helper cells from cytotoxic cells (3). Although there were persistent reports of heterogeneity in the helper T-cell compartment (reviewed below), only relatively recently were distinct types of helper cells resolved. In this review we describe the differences between two types of cloned helper T cells, defined primarily by differences in the pattern of lymphokines ynthesized, and we also discuss the different functions of the two types of cells and their lymphokines. Patterns of lymphokine synthesis are convenient and explicit markers to describe T-cell subclass differences, and evidence increases that many of the functions of helper T cells are predicted by the functions of the lymphokines that they synthesize after activation by antigen and presenting cells. The separation of many mouse helper T-cell clones into these two distinct types is now well established, but their origin in normal T-cell populations is still not clear. Further divisions of helper T cells may have to be recognized before a complete picture of helper T-cell function can be obtained.

TH1 and TH2 cells: different patterns of lymphokine secretion lead to different functional properties.

Biologic basis for interleukin-1 in disease

In the present study we demonstrate that human monocytes activated by lipopolysaccharides (LPS) were able to produce high levels of interleukin 10 (IL-10), previously designated cytokine synthesis inhibitory factor (CSIF), in a dose dependent fashion. IL-10 was detectable 7 h after activation of the monocytes and maximal levels of IL-10 production were observed after 24-48 h. These kinetics indicated that the production of IL-10 by human monocytes was relatively late as compared to the production of IL-1 alpha, IL-1 beta, IL-6, IL-8, tumor necrosis factor alpha (TNF alpha), and granulocyte colony-stimulating factor (G-CSF), which were all secreted at high levels 4-8 h after activation. The production of IL-10 by LPS activated monocytes was, similar to that of IL-1 alpha, IL-1 beta, IL-6, IL-8, TNF alpha, granulocyte-macrophage colony-stimulating factor (GM-CSF), and G-CSF, inhibited by IL-4. Furthermore we demonstrate here that IL-10, added to monocytes, activated by interferon gamma (IFN-gamma), LPS, or combinations of LPS and IFN-gamma at the onset of the cultures, strongly inhibited the production of IL-1 alpha, IL-1 beta, IL-6, IL-8, TNF alpha, GM-CSF, and G-CSF at the transcriptional level. Viral-IL-10, which has similar biological activities on human cells, also inhibited the production of TNF alpha and GM-CSF by monocytes following LPS activation. Activation of monocytes by LPS in the presence of neutralizing anti-IL-10 monoclonal antibodies resulted in the production of higher amounts of cytokines relative to LPS treatment alone, indicating that endogenously produced IL-10 inhibited the production of IL-1 alpha, IL-1 beta, IL-6, IL-8, TNF alpha, GM-CSF, and G-CSF. In addition, IL-10 had autoregulatory effects since it strongly inhibited IL-10 mRNA synthesis in LPS activated monocytes. Furthermore, endogenously produced IL-10 was found to be responsible for the reduction in class II major histocompatibility complex (MHC) expression following activation of monocytes with LPS. Taken together our results indicate that IL-10 has important regulatory effects on immunological and inflammatory responses because of its capacity to downregulate class II MHC expression and to inhibit the production of proinflammatory cytokines by monocytes.

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Interleukin 10(IL-10) inhibits cytokine synthesis by human monocytes: an autoregulatory role of IL-10 produced by monocytes.

Publisher Summary This chapter investigates the anatomy and taxonomy of protein structures. A protein is a polypeptide chain made up of amino acid residues linked together in a definite sequence. Amino acids are “handed,” and naturally occurring proteins contain only L-amino acids. A simple mnemonic for that purpose is the “corncrib.” The sequence of side chains determines all that is unique about a particular protein, including its biological function and its specific three-dimensional structure. The major possible routes to knowledge of three-dimensional protein structure are prediction from the amino acid sequence and analysis of spectroscopic measurements such as circular dichroism, laser Raman spectroscopy, and nuclear magnetic resonance. The analysis and discussion of protein structure is based on the results of three-dimensional X-ray crystallography of globular proteins. The basic elements of protein structures are discussed. The most useful level at which protein structures are to be categorized is the domain, as there are many cases of multiple-domain proteins in which each separate domain resembles other entire smaller proteins. The simplest type of stable protein structure consists of polypeptide backbone wrapped more or less uniformly around the outside of a single hydrophobic core. The outline of the taxonomy is also provided in the chapter.

The anatomy and taxonomy of protein structure.

A method is presented for locating protein antigenic determinants by analyzing amino acid sequences in order to find the point of greatest local hydrophilicity. This is accomplished by assigning each amino acid a numerical value (hydrophilicity value) and then repetitively averaging these values along the peptide chain. The point of highest local average hydrophilicity is invariably located in, or immediately adjacent to, an antigenic determinant. It was found that the prediction success rate depended on averaging group length, with hexapeptide averages yielding optimal results. The method was developed using 12 proteins for which extensive immunochemical analysis has been carried out and subsequently was used to predict antigenic determinants for the following proteins: hepatitis B surface antigen, influenza hemagglutinins, fowl plague virus hemagglutinin, human histocompatibility antigen HLA-B7, human interferons, Escherichia coli and cholera enterotoxins, ragweed allergens Ra3 and Ra5, and streptococcal M protein. The hepatitis B surface antigen sequence was synthesized by chemical means and was shown to have antigenic activity by radioimmunoassay.

https://www.pnas.org/content/pnas/78/6/3824.full.pdf

Prediction of protein antigenic determinants from amino acid sequences.

Two distinct but distantly related complementary DNAs encoding proteins sharing human interleukin-1 (IL-1) activity (termed IL-1 alpha and IL-1 beta), were isolated from a macrophage cDNA library. The primary translation products of the genes are 271 and 269 amino acids long, although expression in Escherichia coli of the carboxy-terminal 159 and 153 amino acids produces IL-1 biological activity.

Cloning, sequence and expression of two distinct human interleukin-1 complementary DNAs

A small hydrophilic peptide of eight amino acids (AspTyrLysAspAspAspAspLys) was engineered onto the N-terminus of a variety of recombinant lymphokines for the purpose of aiding in their detection and purification from yeast supernatants or E. coli extracts. An antibody specific for the first four amino acids of this sequence was used as a detection reagent and for immunoaffinity purification of products under mild conditions. Because of the small size of the peptide moiety and its hydrophilic nature, the proteins were unaffected by its presence and retained a high level of biological activity. In addition, it was possible to remove the peptide via an enzymatic cleavage procedure using enterokinase.

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A Short Polypeptide Marker Sequence Useful for Recombinant Protein Identification and Purification.

An immunoglobulin is provided which consists essentially of a mono-specific, hetero-molecular antibody which is mono-specific to a single antigenic or allergenic determinant. The antibody is specific to the H-epitope of a protein antigen or allergen. The H-epitope is defined by a sequence of at least six amino acids corresponding to the sequence of such amino acids in the protein antigen or allergen where the greatest local average hydrophilicity of the protein antigen or allergen is found.

Identification and preparation of epitopes on antigens and allergens on the basis of hydrophilicity

Interleukin-1 (IL-1) is a factor that can induce proliferation of murine T lymphocytes1,2 and can elicit a variety of other biological responses These include bone resorption3, fibroblast proliferation4, acute phase protein release from hepatocytes5, cartilage breakdown6 and fever7 This spectrum of activities is consistent with a role for IL-1 as a mediator of inflammation Recently, sequence data have shown that there are at least two members of the IL-1 family; these distantly related proteins have been termed IL-1α and IL-1β8–11 We have found previously that both murine T cells and fibroblasts possess a relative molecular mass (Mr) ∼80,000 (80K) plasma membrane receptor for human IL-1β12,13 We show here that the receptor for IL-1α on both murine and human cells is identical to that for IL-1β This result raises the issue of what separation, if any, there might be between the biological activities of IL-1α and IL-1β

Thomas P. Hopp

Papers

Prediction of protein antigenic determinants from amino acid sequences.

Cloning, sequence and expression of two distinct human interleukin-1 complementary DNAs

A Short Polypeptide Marker Sequence Useful for Recombinant Protein Identification and Purification.

Identification and preparation of epitopes on antigens and allergens on the basis of hydrophilicity

The cell surface receptors for interleukin-1α and interleukin-1β are identical