Alternatively spliced pp52 mRNA in nonlymphoid stromal cells

Area of Science:

• Molecular Biology
• Cell Biology
• Biochemistry

Background:

• The 52-kDa phosphoprotein (also known as lymphocyte-specific gene 1 and WP34) is a protein involved in lymphocyte function.
• It is phosphorylated and binds calcium, suggesting a role in signal transduction pathways within lymphocytes.

Purpose of the Study:

• To investigate the expression and potential alternative splicing of the 52-kDa phosphoprotein gene in different cell types.
• To characterize the molecular differences between lymphoid and nonlymphoid forms of the protein.

Main Methods:

• Analysis of mRNA transcripts in B lymphocytes, T cells, and nonlymphoid cell lines (myocytes, stromal cells, fibroblasts).
• Cloning and sequencing of a full-length cDNA (S37) from a stromal cell line using conventional and PCR-based methods.
• Comparison of nucleotide and amino acid sequences between lymphocyte-derived and stromal cell-derived cDNA clones.

Main Results:

• Lymphoid cells express a 1.6-kb mRNA, while nonlymphoid cells express alternatively spliced 2.0-kb and 2.8-kb mRNA variants.
• A 2.0-kb cDNA clone (S37) from stromal cells encodes a protein identical to the lymphocyte form up to amino acid residue 24.
• Sequence differences in the 5' region and N-terminal amino acids indicate alternative exon utilization, leading to distinct protein isoforms.

Conclusions:

• The 52-kDa phosphoprotein gene is subject to alternative splicing.
• Tissue-specific mechanisms generate distinct mRNA forms in lymphoid and mesoderm-derived nonlymphoid cell lineages.
• These findings suggest differential roles for 52-kDa phosphoprotein isoforms in various cell types.