Imbalances in protein homeostasis caused by mutant desmin

AIMS

We investigated newly generated immortalized heterozygous and homozygous R349P desmin knock-in myoblasts in conjunction with the corresponding desminopathy mice as models for desminopathies to analyse major protein quality control processes in response to the presence of R349P mutant desmin.

METHODS

We used hetero- and homozygous R349P desmin knock-in mice for analyses and for crossbreeding with p53 knock-out mice to generate immortalized R349P desmin knock-in skeletal muscle myoblasts and myotubes. Skeletal muscle sections and cultured muscle cells were investigated by indirect immunofluorescence microscopy, proteasomal activity measurements and immunoblotting addressing autophagy rate, chaperone-assisted selective autophagy and heat shock protein levels. Muscle sections were further analysed by transmission and immunogold electron microscopy.

RESULTS

We demonstrate that mutant desmin (i) increases proteasomal activity, (ii) stimulates macroautophagy, (iii) dysregulates the chaperone assisted selective autophagy and (iv) elevates the protein levels of αB-crystallin and Hsp27. Both αB-crystallin and Hsp27 as well as Hsp90 displayed translocation patterns from Z-discs as well as Z-I junctions, respectively, to the level of sarcomeric I-bands in dominant and recessive desminopathies.

CONCLUSIONS

Our findings demonstrate that the presence of R349P mutant desmin causes a general imbalance in skeletal muscle protein homeostasis via aberrant activity of all major protein quality control systems. The augmented activity of these systems and the subcellular shift of essential heat shock proteins may deleteriously contribute to the previously observed increased turnover of desmin itself and desmin-binding partners, which triggers progressive dysfunction of the extrasarcomeric cytoskeleton and the myofibrillar apparatus in the course of the development of desminopathies.

[Whiplash injuries of the cervical spine. Neurologic contribution to diagnosis. Therapy and expert evaluation]

The cervical spine is an extremely complex functional unit and has always been the subject of impassioned discussions among surgeons, orthopedic specialists and neurologists. In the presence of injuries affecting this section of the spine, which sometimes have grave consequences--including implications for legal insurance aspects, neurologists are usually at the end of the line when it comes to diagnosis and treatment. In fact, in view of the clinical and technical neurophysiological options available to neurologists, it would be desirable for them to be involved as early as possible. In this paper the relative value of neurology, compared with orthopedics and surgery, in the diagnosis and treatment of whiplash injury to the cervical spine is discussed. The newer options available--particularly in neurophysiology--are highlighted, as are the differential diagnosis and problems concerned with official expert assessments, which also involve other specialties.

Endothelial seeding of compliant polyurethane vascular graft material

Compliance was measured in a new compliant polyurethane vascular graft material and in polytetrafluoroethylene (PTFE) graft material using an ultrasonic device; attachment of indium-111 oxine-labelled human endothelial cells to both surfaces with a range of surface coatings was assessed. Compliant polyurethane was six to eight times more compliant than PTFE (P < 0.01) at all pressures in the range 50-120 mmHg, and endothelial cell attachment to uncoated polyurethane was three times better than to uncoated PTFE at times up to 90 min (P < 0.01). Attachment to polyurethane was also better after blood clot, collagen and fibronectin treatment at times up to 30 min (P < 0.05). Endothelial seeding of compliant graft material may provide a prosthetic vascular substitute with characteristics similar to those of autologous vein.