Peptide cellular

P. S., Strategies toward predicting peptide cellular permeability from computed molecular descriptors, J. Pept. Res., 1999, 53, 355-369. 

Dhein S, Tudyka T Therapeutic potential of antiarrhythmic peptides. Cellular coupling as a new antiarrhythmic target. Drugs 1995 49 851-855. 

It can be deduced from Table 39.1 that most biopharmaceuticals approved to date are monoclonal antibodies and the most common indication is oncology. However, barring oncology, the biopharmaceuticals span an impressive range of indications. In addition to monoclonal antibodies, other prevalent types of biopharmaceuticals are fusion or conjugate proteins, growth factors, replacement enzymes, and peptides. Cellular and tissue therapies are rarer but becoming more prevalent. 

Goodwin JT, Mao B, Vidmar TJ, Conradi RA, and Burton PS. Strategies Toward Predicting Peptide Cellular Permeability from Computed Molecular Descriptors./Pejlihde 1999 53 355-369. 

Most reactions in cells are carried out by enzymes [1], In many instances the rates of enzyme-catalysed reactions are enhanced by a factor of a million. A significantly large fraction of all known enzymes are proteins which are made from twenty naturally occurring amino acids. The amino acids are linked by peptide bonds to fonn polypeptide chains. The primary sequence of a protein specifies the linear order in which the amino acids are linked. To carry out the catalytic activity the linear sequence has to fold to a well defined tliree-dimensional (3D) stmcture. In cells only a relatively small fraction of proteins require assistance from chaperones (helper proteins) [2]. Even in the complicated cellular environment most proteins fold spontaneously upon synthesis. The detennination of the 3D folded stmcture from the one-dimensional primary sequence is the most popular protein folding problem. 

Much of protein engineering concerns attempts to explore the relationship between protein stmcture and function. Proteins are polymers of amino acids (qv), which have general stmcture +H3N—CHR—COO , where R, the amino acid side chain, determines the unique identity and hence the stmcture and reactivity of the amino acid (Fig. 1, Table 1). Formation of a polypeptide or protein from the constituent amino acids involves the condensation of the amino-nitrogen of one residue to the carboxylate-carbon of another residue to form an amide, also called peptide, bond and water. The linear order in which amino acids are linked in the protein is called the primary stmcture of the protein or, more commonly, the amino acid sequence. Only 20 amino acid stmctures are used commonly in the cellular biosynthesis of proteins (qv). 

Cellular protein biosynthesis involves the following steps. One strand of double-stranded DNA serves as a template strand for the synthesis of a complementary single-stranded messenger ribonucleic acid (mRNA) in a process called transcription. This mRNA in turn serves as a template to direct the synthesis of the protein in a process called translation. The codons of the mRNA are read sequentially by transfer RNA (tRNA) molecules, which bind specifically to the mRNA via triplets of nucleotides that are complementary to the particular codon, called an anticodon. Protein synthesis occurs on a ribosome, a complex consisting of more than 50 different proteins and several stmctural RNA molecules, which moves along the mRNA and mediates the binding of the tRNA molecules and the formation of the nascent peptide chain. The tRNA molecule carries an activated form of the specific amino acid to the ribosome where it is added to the end of the growing peptide chain. There is at least one tRNA for each amino acid. 

The primary cellular function of mRNA is to direct biosynthesis of the thousands of diverse peptides and proteins required by an organism—perhaps 100,000 in a human. The mechanics of protein biosynthesis take place on ribosomes, small granular particles in the cytoplasm of a cell that consist of about 60% ribosomal RNA and 40% protein. 

The predominant cell type in the pancreatic islets of Langerhans. The main secretory product of the (3 -cell is the peptide hormone insulin which has vital actions for the control of nutrient homeostasis and cellular differentiation. 

Somatostatin is a regulatory cyclic peptide, which has originally been described as a hypothalamic growth hormone release-inhibiting factor. It is produced throughout the central nervous system (CNS) as well as in secretoty cells of the periphery and mediates its regulatory functions on cellular processes such as neurotransmission, smooth muscle contraction, secretion and cell proliferation via a family of seven transmembrane domain G-protein-coupled receptors termed sstx 5. 

The VACM-1 receptor is a membrane-associated protein with a single putative transmembrane domain that binds selectively AVP (XD — 2 nM), but cannot discriminate between VXR and V2R analogues. It is expressed in endothelial and medullary collecting duct cells and upon stimulation by AVP. It induces a mobilization of cytosolic-free Ca2+, decreases cAMP production and inhibits cellular growth via MAPK phosphorylation and p53 expression. The mechanism of action and physiological functions of this new receptor are not well understood, but it seems to participate in the regulation of AVP induced signal transduction pathways or of a yet unidentified peptide. 

O Neill, C., Riddle, P., Rosengurt, E. (1985). Stimulating the proliferation of quiescent 3T3 fibroblasts by peptide growth factors or by agents which elevate cellular cyclic AMP level has opposite effects on motility. Expt. Cell Res. 156.65-78. 

The secretion of extracellular matrix proteins is also a function of smooth muscle cells but, since it occurs concurrently with other activities, it does not seem to constitute a physiological state. However, the fraction of the cellular resources which are devoted to it must be regulated these regulatory mechanisms are virtually unknown. In addition, it should be anticipated that autocrine activity occurs as well, involving peptides, prostaglandins, cytokines, and nitric oxide. 

To obtain an increased intrinsic capacity to transgress biological membranes, a number of different modifications have been introduced to PNA. These modifications include conjugation of PNA to Hpophilic moieties [51, 97, 98], conjugation of PNA to certain so-caUed ceU-penetrating peptides [49, 55, 56, 66, 99-102] and conjugation to different moieties, which are supposed to be internahzed by specific cellular receptors [48, 103-105]. The work on cellular dehvery of PNA is, like the related work on ex vivo and in vivo effects of PNA, very difficult to summarize conclusively. First of all, the pronounced diversity of the reporter systems employed makes it impossible to directly compare the studies. Secondly, the widespread use of fluorescence studies in spite of the many inherent pitfalls of this technique makes it sometimes difficult to judge even qualitatively whether a presented result actually indicates cellular uptake. We have recently published a comprehensive review on cellular dehvery of PNA [82], with a more detailed assessment of the PNA dehvery hterature. 

Hamilton S. E., Simmons C.G., Kathir-iya I.S., Corey D.R. Cellular delivery of peptide nucleic acids and inhibition of human telomerase. Chem. Biol. 1999 6 343-351. 

Boffa L.C., Scarf S., Marian M.R., Dai40nte G, Allfrey V.G., Benatti U., Morris O. L. Dihydrotestosterone as a selective cellular/nuclear localization vector for anti-gene peptide nucleic acid in prostatic carcinoma cells. Cancer Res. 2000 60 2258-2262. 

Koppelhus U., Nielsen P.E. Cellular delivery of peptide nucleic acid (PNA). Adv. Drug Deliv. Rev. 2003 55 267-280... 

Ljungstrom T., Knudsen H., Nielsen P.E. Cellular uptake of adamantyl conjugated peptide nucleic acids. Bioconjug. 

Koppelhus U., Awasthi S.K., Zachar V., Holst H.U., Ebbesen P., Nielsen P. E. Cell-dependent differential cellular uptake of PNA, peptides, and PNA-pep-tide conjugates. Antisense Nucleic Acid Drug Dev. 2002 12 51-63. 

Basu S., Wickstrom E. Synthesis and characterization of a peptide nucleic acid conjugated to a D-peptide analog of insu-lin-like growth factor 1 for increased cellular uptake. Bioconjug. Chem. 1997 8 481-488. 

In terms of their molecular structures, the nucleotide and protein realms are usually considered to be rather independent of each other. However, these two families of molecules are covalently linked in the translational aminoacyl- RNAs and ribonucleoproteins as well as in the nucleoproteins involved in cellular and viral replication. In these hybrid biomolecules, a (deoxy)ribose phosphate moiety serves as the structural connection between the nucleoside and peptide moieties. 

Oehlke and coworkers have described the cellular uptake properties of a simple a-hehcal amphipathic model peptide sequence (Lys-Leu-Ala-Leu-Lys-Leu-Ala-Leu-Lys-Ala-Leu-Lys-Ala-Ala-Leu-Lys-Leu-Ala) in the context of a drug delivery vehicle [72]. On the basis of the data presented, it was proposed that non-endocytosis mechanism(s) were involved in the uptake into mammalian cells. The similarity between our b2 aPNA-sequence to that of this amphipathic model peptide makes it tempting to suggest that a similar uptake mechanism is involved in the cellular uptake of aPNAs. Further experimentation is necessary to test this hypothesis. 

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