PTPRN2 is a membrane protein of neuroendocrine secretory vesicles that traffics between secretory granules and the plasma membrane. It regulates vesicle accumulation and secretion and has a phosphatase-like intracellular domain. Conventional phosphoprotein activity is impaired, whereas phosphoinositide phosphatase activity and regulation of membrane PI(4,5)P2 have been reported in mammalian cells.
The 1996 cloning report states that recombinant IAR/PTPRN2 has phosphatase activity, but its abstract does not name the substrate. Later human cell work explicitly distinguishes lack of phosphoprotein-substrate activity from phosphoinositide phosphatase activity and tests the effect of a catalytic-domain mutant on migration and metastasis. Vesicle accumulation, insulin/neurotransmitter release, and membrane phosphoinositide regulation are not interchangeable with protein tyrosine dephosphorylation. Conversely, a biological-process annotation can describe regulation through another enzyme: losing intrinsic protein phosphatase activity alone does not refute all participation in protein dephosphorylation. The exact experimental annotation therefore remains unresolved while the inappropriate electronic intrinsic protein-phosphatase terms can be challenged.
From PMID:26620550(https://pubmed.ncbi.nlm.nih.gov/26620550/):
As a transmembrane protein, PTPRN2 shuttles between secretory vesicles and the plasma membrane.
The exact target is A0A9L0T4W6, not an arbitrary horse record with a matching name. The reproducible paired-sequence analysis records identity, coverage and internal gaps. It supports homology but is not a reciprocal orthology test. Molecular properties are transferred only with the relevant domain, targeting and paralog constraints. The prediction-time sequence is not independently verified.
The following annotation scopes need source-specific follow-up: ficolin-1-rich granule membrane, protein dephosphorylation, signaling receptor complex, transmembrane receptor protein tyrosine phosphatase activity. Experimental annotations are not removed merely because a cached abstract omits the gene or a specific assay. High-throughput protein-binding rows require their actual partner or complex context before replacement with an informative molecular function.