A Journey with LGMD: From Protein Abnormalities to Patient Impact.

The limb-girdle muscular dystrophies (LGMD) are a collection of genetic diseases united in their phenotypical expression of pelvic and shoulder area weakness and wasting. More than 30 subtypes have been identified, five dominant and 26 recessive. The increase in the characterization of new genotypes in the family of LGMDs further adds to the heterogeneity of the disease. Meanwhile, better understanding of the phenotype led to the reconsideration of the disease definition, which resulted in eight old subtypes to be no longer recognized officially as LGMD and five new diseases to be added to the LGMD family. The unique variabilities of LGMD stem from genetic mutations, which then lead to protein and ultimately muscle dysfunction. Herein, we review the LGMD pathway, starting with the genetic mutations that encode proteins involved in muscle maintenance and repair, and including the genotype-phenotype relationship of the disease, the epidemiology, disease progression, burden of illness, and emerging treatments.

A cyclic pentapeptide derived from the second EGF-like domain of Factor VII is an inhibitor of tissue factor dependent coagulation and thrombus formation.

We have previously reported the finding of a cyclic dodecapeptide representing loop I of the second EGF-like domain of FVII, which inhibited TF-dependent FX activation (Orning et al. 1997). The biological activity was localized to the tripeptide motif, Glu-Gln-Tyr. We have now synthesized a cyclic analog of this motif, Cys-Glu-Gln-Tyr-Cys (PN7051), evaluated its anticoagulant and antithrombotic properties and performed a detailed structural characterization of the peptide. PN7051 is a dose-dependent inhibitor of TF-dependent FX activation and coagulation of plasma with IC50 values of 10+/-2 microM and 1.3+/-0.2 mM, respectively. It shows inhibitory efficacy on acute thrombus formation in an ex vivo model of human thrombosis using native blood. Fibrin deposition, platelet-fibrin adhesion, platelet-thrombus formation, and thrombin-antithrombin complex formation were all inhibited by PN7051 at IC50 values between 0.3 and 0.7 mM. The cyclic peptide is a non-competitive inhibitor of FX activation with no significant active-site effects on FXa or FVIIa, indicating it affects FVII/TF/FX complex formation and function. Studies on the structure activity relationship revealed that Gln3-Tyr4, but not Glu2 were of importance for inhibition. In line with biological results, NMR measurements of PN7051 suggested that the Gln and Tyr residues configure a structural feature that contributes to the anticoagulant activity. Modeling of the Glu99Gln100Tyr101 motif in FVII and comparison with the solution structure of PN705 I suggest that the cyclic pentapeptide exerts its antithrombotic effect by interfering with the docking of Tyr101 into a hydrophobic pocket in the catalytic domain thereby disrupting an essential interaction between the second EGF-like and the catalytic domains of FVII.