Proteolytic enzymes

About: Proteolytic enzymes is a research topic. Over the lifetime, 23096 publications have been published within this topic receiving 835544 citations.

Destruction of sodium conductance inactivation in squid axons perfused with pronase.

Abstract: We have studied the effects of the proteolytic enzyme Pronase on the membrane currents of voltage-clamped squid axons Internal perfusion of the axons with Pronase rather selectively destroys inactivation of the Na conductance ( g Na) At the level of a single channel, Pronase probably acts in an all-or-none manner: each channel inactivates normally until its inactivation gate is destroyed, and then it no longer inactivates Pronase reduces g¯ Na, possibly by destroying some of the channels, but after removal of its inactivation gate a Na channel seems no longer vulnerable to Pronase The turn-off kinetics and the voltage dependence of the Na channel activation gates are not affected by Pronase, and it is probable that the enzyme does not affect these gates in any way Neither the K channels nor their activation gates are affected in a specific way by Pronase Tetrodotoxin does not protect the inactivation gates from Pronase, nor does maintained inactivation of the Na channels during exposure to Pronase Our results suggest that the inactivation gate is a readily accessible protein attached to the inner end of each Na channel It is shown clearly that activation and inactivation of Na channels are separable processes, and that Na channels are distinct from K channels

All roads lead to disconnection? – Traumatic axonal injury revisited

Abstract: Traumatic brain injury (TBI) evokes widespread/diffuse axonal injury (TAI) significantly contributing to its morbidity and mortality. While classic theories suggest that traumatically injured axons are mechanically torn at the moment of injury, studies in the last two decades have not supported this premise in the majority of injured axons. Rather, current thought considers TAI a progressive process evoked by the tensile forces of injury, gradually evolving from focal axonal alteration to ultimate disconnection. Recent observations have demonstrated that traumatically induced focal axolemmal permeability leads to local influx of Ca2+ with the subsequent activation of the cysteine proteases, calpain and caspase, that then play a pivotal role in the ensuing pathogenesis of TAI via proteolytic digestion of brain spectrin, a major constituent of the subaxolemmal cytoskeletal network, the “membrane skeleton”. In this pathological progression this local Ca2+ overloading with the activation of calpains also initiates mitochondrial injury that results in the release of cytochrome-c, with the activation of caspase. Both the activated calpain and caspases then participate in the degradation of the local axonal cytoskeleton causing local axonal failure and disconnection. In this review, we summarize contemporary thought on the pathogenesis of TAI, while discussing the potential diversity of pathological processes observed within various injured fiber types. The anterograde and retrograde consequences of TAI are also considered together with a discussion of various experimental therapeutic approaches capable of attenuating TAI.

Peptide linkers for improved oligonucleotide delivery

Abstract: A covalently linked conjugate of an oligonucleotide (ODN) with a peptide and a carrier or targeting ligand (ODN-peptide-carrier) includes a therapeutic oligonucleotide which is capable of selectively binding to a target sequence of DNA, RNA or protein inside a target cell. The ODN is covalently linked to a peptide which is capable of being cleaved by proteolytic enzymes inside the target cell. The peptide, in turn is covalently linked to a carrier or targeting ligand moiety which facilitates delivery of the entire ODN-peptide-carrier conjugate into the cell, and preferably into a specific target tissue type. Inside the cell, the peptide is cleaved, releasing the ODN which, by binding to the target DNA, RNA or protein sequence, brings about a beneficial result.

HIV-1 drug resistance in newly infected individuals.

Abstract: ContextThere is concern that the widespread use of antiretroviral drugs to treat human immunodeficiency virus 1 (HIV-1) infection may result in the increased transmission of drug-resistant virus.ObjectiveTo determine the prevalence of drug resistance–conferring mutations and phenotypic resistance to antiretroviral agents in a cohort of individuals newly infected with HIV-1.DesignCase series with genetic analyses of the HIV-1 plasma-derived pol gene using reverse transcriptase polymerase chain reaction followed by direct sequencing of polymerase chain reaction products. Phenotypic analysis was performed with a recombinant virus assay.Setting and PatientsEighty individuals referred, on average, 1.7 months after infection with HIV-1 to the Aaron Diamond AIDS Research Center between July 1995 and April 1999. Subjects were from large urban areas (65 from New York, NY; 11 from Los Angeles, Calif); 60 (75%) were white, and 75 (93.8%) were homosexual men.Main Outcome MeasuresPrevalence of known resistance-conferring genotypes and reduced susceptibility to individual antiviral agents by phenotype.ResultsThirteen individuals (16.3%) had genotypes associated with drug resistance to any antiretroviral agent. Virus with known resistance-conferring mutations to any nucleoside reverse transcriptase inhibitors was found in 10 individuals, to any nonnucleoside reverse transcriptase inhibitors in 6 subjects, and to any protease inhibitors in 2 cases. Multidrug-resistant virus was identified in 3 individuals (3.8%). Extensive polymorphism in the protease gene was identified. Interpretation of genotypes and phenotypes was concordant in 57 (85%) of the 67 cases in which both studies were performed.ConclusionThe prevalence of HIV-1 variants with known resistance-conferring genotypes to any antiretroviral agent in this cohort of 80 newly infected individuals is 16.3%. These data support expanded use of resistance testing in the setting of primary HIV-1 infection. Clinical trials should be initiated to establish whether therapy guided by resistance testing, compared with the use of empirical triple combination antiretroviral therapy, provides additional virological and immunological benefit when treating primary HIV-1 infection. Further efforts to expand the study of transmission of drug-resistant HIV-1 variants, particularly in cohorts with different epidemiological profiles, are indicated.