Isoform 2 of 1-phosphatidylinositol 4,5-bisphosphate phosphodiesterase delta-1

PLCD1 isoform 2 encodes phosphatidylinositol 4,5-bisphosphate phosphodiesterase delta-1, an enzyme involved in phosphoinositide signaling (UniProt: P51178-2). This 777-amino acid protein mediates the hydrolysis of PIP2 to generate the second messengers inositol 1,4,5-trisphosphate and diacylglycerol, which regulate calcium mobilization and protein kinase C activation in cellular signaling cascades.

PLCD1 is expressed across neural and non-neural tissues where phosphoinositide signaling is essential for cellular communication and cytoskeletal dynamics. The UniProt record does not list curated disease associations; however, phospholipase C isoforms have documented roles in neuronal excitability and synaptic transmission.

In Alzheimer's disease, PLCD1 isoform 2 shows increased abundance in post-mortem AD brain tissue relative to age-matched controls (Chaparral AD proteomics: mean log2FC +0.779, up-regulated), as measured by TMT-labeled quantitative proteomics across subcellular fractions. This elevation may reflect compensatory phosphoinositide signaling changes or altered synaptic function associated with AD neurodegeneration, though mechanistic interpretation requires further investigation.