The lysosome-associated membrane protein LAMP-2 was evaluated in this study following the report that the related protein, LAMP-1, was increased in many, but not all, LSDs (12).
It was noted previously in the LAMP-1 assay (12) that there was an interaction of LAMP-1 with plasma proteins, which caused a slight decrease in the measured concentration of exogenous LAMP-1 that was added to plasma.
The mean concentration of LAMP-2 in unaffected plasma was 1.21 mg/L, fourfold higher than LAMP-1, which was 0.31 mg/L.
The significant correlation between the amount of LAMP-1 and LAMP-2 in blood spots from newborns and plasma from both unaffected and LSD-affected individuals demonstrates that these are not independent variables and, as such, that there would be no advantage to screening for both markers.
This has been discussed previously (12); however, it is still unknown why LAMP-1 and LAMP-2 are increased in some disorders and not others.
The distributions of both LAMP-1 and LAMP-2 in the unpartitioned newborn population were characteristically skewed towards the high concentrations; this will produce a large number of false positives arising from the primary screen.
Diagnosis of lysosomal storage disorders: evaluation of a lysosome-associated membrane protein LAMP-1 as a diagnostic marker.
The genes of major lysosomal membrane glycoproteins, lamp-1 and lamp-2.
The lysosomal membrane glycoproteins Lamp-1 and Lamp-2 are present in mobilizable organelles, but are absent from the azurophil granules of human neutrophils.