Population Structure among Mycobacterium tuberculosis Isolates from Pulmonary Tuberculosis Patients in Colombia

Background

Phylogeographic composition of M. tuberculosis populations reveals associations between lineages and human populations that might have implications for the development of strategies to control the disease. In Latin America, lineage 4 or the Euro-American, is predominant with considerable variations among and within countries. In Colombia, although few studies from specific localities have revealed differences in M. tuberculosis populations, there are still areas of the country where this information is lacking, as is a comparison of Colombian isolates with those from the rest of the world.

Principal Findings

A total of 414 M. tuberculosis isolates from adult pulmonary tuberculosis cases from three Colombian states were studied. Isolates were genotyped using IS6110-restriction fragment length polymorphism (RFLP), spoligotyping, and 24-locus Mycobacterial interspersed repetitive units variable number tandem repeats (MIRU-VNTRs). SIT42 (LAM9) and SIT62 (H1) represented 53.3% of isolates, followed by 8.21% SIT50 (H3), 5.07% SIT53 (T1), and 3.14% SIT727 (H1). Composite spoligotyping and 24-locus MIRU- VNTR minimum spanning tree analysis suggest a recent expansion of SIT42 and SIT62 evolved originally from SIT53 (T1). The proportion of Haarlem sublineage (44.3%) was significantly higher than that in neighboring countries. Associations were found between M. tuberculosis MDR and SIT45 (H1), as well as HIV-positive serology with SIT727 (H1) and SIT53 (T1).

Conclusions

This study showed the population structure of M. tuberculosis in several regions from Colombia with a dominance of the LAM and Haarlem sublineages, particularly in two major urban settings (Medellín and Cali). Dominant spoligotypes were LAM9 (SIT 42) and Haarlem (SIT62). The proportion of the Haarlem sublineage was higher in Colombia compared to that in neighboring countries, suggesting particular conditions of co-evolution with the corresponding human population that favor the success of this sublineage.     

The product of the cbl oncogene forms stable complexes in vivo with endogenous Crk in a tyrosine phosphorylation-dependent manner.

The cellular homologs of the v-Crk oncogene product are composed exclusively of Src homology region 2 (SH2) and SH3 domains. v-Crk overexpression in fibroblasts causes cell transformation and elevated tyrosine phosphorylation of specific cellular proteins. Among these proteins is a 130-kDa protein, identified as p130cas, that forms a stable complex in vivo with v-Crk. We have explored the role of endogenous Crk proteins in Bcr-Abl-transformed cells. In the K562 human chronic myelogenous leukemia cell line, p130cas is not tyrosine phosphorylated or bound to Crk. Instead, Crk proteins predominantly associate with the tyrosine-phosphorylated proto-oncogene product of Cbl. In vitro analysis showed that this interaction is mediated by the SH2 domain of Crk and can be inhibited with a phosphopeptide containing the Crk-SH2 binding motif. In NIH 3T3 cells transformed by Bcr-Abl, c-Cbl becomes strongly tyrosine phosphorylated and associates with c-Crk. The complex between c-Crk and c-Cbl is also seen upon T-cell receptor cross-linking or with the transforming, tyrosine-phosphorylated c-Cbl. These results indicate that Crk binds to c-Cbl in a tyrosine phosphorylation-dependent manner, suggesting a physiological role for the Crk-c-Cbl complex in Bcr-Abl tyrosine phosphorylation-mediated transformation.     

Spatial determinants of specificity in insulin action

Insulin is a potent stimulator of intermediary metabolism, however the basis for the remarkable specificity of insulin's stimulation of these pathways remains largely unknown. This review focuses on the role compartmentalization plays in insulin action, both in signal initiation and in signal reception. Two examples are discussed: (1) a novel signalling pathway leading to the phosphorylation of the caveolar coat protein caveolin, and (2) a recently identified scaffolding protein, PTG, involved directly in the regulation of enzymes controlling glycogen metabolism.