Trypanosome protozoa, an early lineage of eukaryotic cells, have proteases homologous to mammalian lysosomal cathepsins, but the precursor proteins lack mannose 6-phosphate. Utilizing green fluorescent protein as a reporter, we demonstrate that the carbohydrate-free prodomain of a trypanosome cathepsin L is necessary and sufficient for directing green fluorescent protein to the lysosome/endosome compartment. A proper prodomain/catalytic domain processing site sequence is also required to free the mature protease for delivery to the lysosome/endosome compartment. A nine-amino acid prodomain loop motif, implicated in prodomain-receptor interactions in mammalian cells, is conserved in the protozoa. Site-directed mutagenesis now confirms the importance of this loop to protease trafficking and suggests that a protein motif targeting signal for lysosomal proteases arose early in eukaryotic cell evolution.Sorting of newly translated lysosomal proteases may occur by two different mechanisms. In mammalian cells, the predominant is through the addition of phosphomannosyl residues and targeting to the lysosome pathway by binding to M6P 1 receptors within the Golgi (1). However, transport of lysosomal enzymes in many cells is unaffected by a deficiency in the phosphotransferase, which is required for M6P synthesis (2). M6P-receptor-independent membrane association has been reported for several lysosomal proteins (3). Confirmation and further analysis of a M6P-independent sorting pathway in mammalian cells has been complicated by both the presence of the M6P pathway itself and difficulty in distinguishing effects on protein folding versus protein trafficking when deletional mutants of the protease precursors were analyzed (4, 5). Trypanosoma cruzi and Leishmania mexicana are protozoa (Trypanosoma) representing one of the earliest lineages of eukaryotic cells. They nevertheless express proteases homologous to cathepsins L and B and, unlike yeast, have an organelle ultrastructure more reminiscent of mammalian cells (6). While the cathepsin L-like protease prodomains of these organisms have significant homology to mammalian procathepsin L (e.g. 45% identity for cruzain versus mouse cathepsin L), there are no carbohydrate modifications, so they are unique experimental models for analyzing M6P-independent protein sorting.Trypanosome cysteine proteases are synthesized as precursor proteins with a hydrophobic signal peptide, a 100 -122-amino acid prodomain, a 200 -210-amino acid catalytic domain, and, in most cases, a 100 -130-amino acid carboxyl-terminal domain (7-12). The function of the carboxyl-terminal domain is as yet unknown. Hypotheses that it plays a role in protease inactivation, or in facilitating folding of the catalytic domain, have been ruled out by expression of fully active recombinant proteases without this domain (10). Other proposed functions have included mediating intracellular trafficking of the protease (13), immune evasion (14), and facilitating activity against specific macromolecular substrates (15).The pr...

The Nicaraguan COVID-19 situation is exceptional for Central America. The government restricts testing and testing supplies, and the true extent of the coronavirus crisis remains unknown. Dozens of deaths have been reported among health-care workers. However, statistics on the crisis’ effect on health-care workers and their risk of being infected with SARS-CoV-2 are lacking. We aimed to estimate the prevalence of SARS-CoV-2 infection in health-care workers and to examine correlations with risk factors such as age, sex and comorbidities. Study participants (N = 402, median age 38.48 years) included physicians, nurses and medical assistants, from public and private hospitals, independent of symptom presentation. SARS-CoV-2 was detected on saliva samples using the loop-mediated isothermal amplification assay. A questionnaire was employed to determine subjects’ COVID-19-associated symptoms and their vulnerability to complications from risk factors such as age, sex, professional role and comorbidities. The study was performed five weeks into the exponential growth period in Nicaragua. We discovered that 30.35% of health-care workers participating in our study had been infected with SARS-CoV-2. A large percentage (54.92%) of those who tested positive were asymptomatic and were still treating patients. Nearly 50% of health-care workers who tested positive were under 40, an astonishing 30.33% reported having at least one comorbidity. In our study, sex and age are important risk factors for the probability of testing positive for SARS-CoV-2 with significance being greatest among those between 30 and 40 years of age. In general, being male resulted in higher risk. Our data are the first non-governmental data obtained in Nicaragua. They shed light on several important aspects of COVID-19 in an underdeveloped nation whose government has implemented a herd-immunity strategy, while lacking an adequate healthcare system and sufficient PPE for health-care workers. These data are important for creating policies for containing the spread of SARS-CoV-2.

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Seeking economic growth and job creation to tackle the nation's extreme poverty, the Nicaraguan government awarded a concession to build an interoceanic canal and associated projects to a recently formed Hong Kong based company with no track record or related expertise. This concession was awarded without a bidding process and in advance of any feasibility, socio-economic or environmental impact assessments; construction has begun without this information. The 278 km long interoceanic canal project may result in significant environmental and social impairments. Of particular concern are damage to Lake Cocibolca, a unique freshwater tropical lake and Central America's main freshwater reservoir; damage to regional biodiversity and ecosystems; and socio-economic impacts. Concerned about the possibly irreparable damage to the environment and to native communities, conservationists and the scientific community at large are urging the Nicaraguan government to devise and reveal an action plan to address and mitigate the possible negative repercussions of this interoceanic canal and associated projects. Critical research needs for preparation of a comprehensive benefit-cost analysis for this megaproject are presented.