Identification and Characterization of Allograft Inflammatory Factor 1‐Like (Aif1L) in Skeletal Muscle

Abstract

Skeletal muscle wasting, or atrophy, results from decreased protein synthesis and an associated increase in protein degradation. This shift towards a decrease in protein content of the cell can result from various physiological conditions, including immobilization, denervation, and aging. Muscle RING Finger 1 (MuRF1), an E3 ubiquitin ligase, has been found to be upregulated during almost all conditions of muscle wasting and is believed to play an important role in targeting proteins for degradation. However, preliminary data described in this study provides new evidence that MuRF1's role in the skeletal muscle atrophy cascade is likely more complex and it appears that MuRF1 is necessary for full transcriptional activation of a small subset of neurogenic atrophy‐induced genes, including allograft inflammatory factor 1‐like (Aif1L). Aif1L has been identified as a novel skeletal muscle gene that is upregulated in wild‐type mice, while MuRF1‐null mice show blunted upregulation in response to denervation. Aif1L is predicated to contain an EF‐hand domain, which can act as a calcium ion binding domain. Furthermore, Aif1L has also recently been implicated in regulating actomyosin contractility and filopodial extensions and may play a similar role in muscle cells. To confirm that Aif1L in expressed in muscle cells, qPCR was used to assess the expression levels in cultured muscle cells, while the cDNA of Aif1L was cloned from the C2C12 mouse myoblast cell line and fused with a green fluorescence protein (GFP) tag. C2C12 cells were then transfected with the Aif1L‐GFP expression plasmid in order to localize the Aif1L protein in proliferating myoblast cells. C2C12 cells transiently overexpressing Aif1L fused to GFP showed punctate fluorescence localized to the perinuclear region of the cytoplasm. The results presented here in combination with additional research into the transcriptional regulation and function of Aif1L will help contribute new insight into the molecular genetic mechanisms of skeletal muscle atrophy and may provide a more complete understanding of how MuRF1 may regulate the neurogenic atrophy cascade during muscle wasting.Support or Funding InformationThe work was support by University of North Florida Transformational Learning Opportunity grants and a University of North Florida Foundation Board Grant to D.W.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.