Characterization of novel FcepsilonRII/CD23 isoforms lacking the transmembrane (TM) segment in human cell lines

Area of Science:

• Immunology
• Molecular Biology
• Cell Biology

Background:

• Human Fc epsilon RII/CD23 is a type II transmembrane glycoprotein with two isoforms (a and b).
• Previously identified CD23 transcripts (a' and b') lack exon 3, affecting transmembrane and cytoplasmic domains.
• The protein products of these truncated transcripts were not well characterized.

Purpose of the Study:

• To analyze the protein products of CD23a' and CD23b' transcripts.
• To characterize the expression and potential function of these novel CD23 protein forms.

Main Methods:

• Utilized rabbit polyclonal antibodies against novel amino acid sequences of CD23a' and CD23b'.
• Performed Western blots on COS cells transfected with CD23a' or CD23b' cDNA.
• Conducted in vitro translation assays and analyzed protein glycosylation resistance (Endo H(f), PNGase F).

Main Results:

• CD23a' and CD23b' transcripts were translated into approximately 40 kDa protein molecules.
• These 40 kDa proteins were recognized by antibodies specific to CD23a'/b' and a soluble CD23 fragment antibody.
• Expressed protein products in human cells were specifically recognized by anti-CD23a' and anti-CD23b' antibodies.
• CD23a' and CD23b' molecules were resistant to deglycosylation, indicating post-translational modifications.

Conclusions:

• The a' and b' CD23 transcripts are expressed and translated in human lymphoid cells.
• The resulting 40 kDa cytoplasmic CD23 proteins may have a unique regulatory role in cell surface CD23 expression.