A.P.2: Proteomic profile of cytoplasmic bodies (CB) compared to non-CB aggregates in HMERF associated with mutations in A-band titin

Abstract

Hereditary myopathy with early respiratory failure (HMERF) is caused by A-band titin mutations and characterized by myofibrillar alterations and protein aggregation in skeletal muscle fibers. Our previous studies revealed that the composition of myotilin-positive aggregates is comparable to that seen in myofibrillar myopathies (MFM). However, there are two different types of protein aggregates in HMERF: subsarcolemmal cytoplasmic bodies (CB) with a dense filamentous core and non-CB aggregates. The aim of this study was to compare the proteomic profile of these protein deposits. We used Gomori trichrome stained skeletal muscle sections from two HMERF patients to separately collect CB, non-CB aggregates and intraindividual control samples by laser microdissection and performed a highly sensitive label-free mass spectrometry approach for protein detection and relative quantification based on spectral counting. The proteomic profiles of CB and non-CB aggregates showed a high degree of similarity: XIRP2, desmin, filamin C, N-RAP, nestin, COL6A3, myotilin, sarcosin, αB-crystallin, dystrophin, XIN and aciculin ranked among the most abundant over-represented proteins (ratio >1.5 compared to control samples) in both aggregate types. Peptides assigned to these twelve proteins accounted for 69% (CB) and 75% (non-CB aggregates) of all peptides assigned to over-represented proteins and the individual proportions of these proteins were almost the same. We also detected similarities in less abundant over-represented proteins. Titin was under-represented in CB (ratio 0.81) and in non-CB aggregates (ratio 0.80). In conclusion, our analysis revealed that the proteomic profiles of CB and non-CB aggregates are highly similar in HMERF, especially regarding abundant over-represented proteins, and typical of MFM aggregates.