Complement Component 1, Q Domain Containing Protein 1 (C1qDC1)

The predicted 1,126-amino acid caprin-2 protein shares 2 conserved regions, termed homology region-1 (HR1) and HR2, with caprin-1. Caprin-2 also has a C-terminal C1q-related domain not present in caprin-1. The authors identified multiple caprin-2 splice variants by database analysis.

The long variant, EEG1L, lacks exon 13 and encodes a 1,077-amino acid protein containing an N-terminal nuclear localization sequence, a C-terminal C1q-like domain, and several phosphorylation sites. The short variant, EEG1S, lacks exon 5, resulting in a frameshift and a truncated protein of 279 amino acids. Immunofluorescence confocal microscopy demonstrated cytoplasmic expression of EEG1L, whereas EEG1S was associated with aggregated mitochondria.