Isoforms of human CD46 Produced by Alternative Splicing Adopt Different Quaternary Structures

Abstract

Alternative splicing can produce multiple mRNA transcripts from a single gene sequence, thereby expanding the number of protein sequences encoded by the genome of a cell. Protein isoforms from alternative splicing may have different functions owing to their different sequences, but examples of alternative splicing producing isoforms with different structures are lacking. CD46 (membrane cofactor protein) is a cell surface glycoprotein that helps protect human cells from destruction by the complement system and a receptor for several human pathogens. It is alternatively spliced into two main isoforms in the extracellular region (BC and C) that differ by the presence or absence of 15 amino acids. Based on existing structural data, we hypothesized that the C isoforms of CD46 form oligomers while the BC isoforms exist as monomers on the cell surface. Proteins on the HeLa cervical cell surface were treated using a membrane‐impermeable crosslinker, then subjected to denaturing gel electrophoresis and western blotting. HeLa cells express both BC and C isoforms of CD46, but only the C isoform changed its electrophoretic mobility to a higher molecular weight after crosslinking. A549 lung epithelial cells express only the BC isoforms, and the molecular weights of their CD46 proteins were unaffected by the crosslinker. These results indicate that CD46 can exist as monomeric and oligomeric spliceoforms. We show that alternative splicing can produce proteins with different quaternary structures from the same gene.Support or Funding InformationFunded by University of Richmond School of Arts & SciencesThis abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.