LAMP proteins are involved in lysosomal function and intracellular trafficking. During a bioinformatics-based search for lysosome-associated molecules, Philippe Pierre and co-workers have identified brain-associated LAMP-like molecule (BAD-LAMP), a new member of the LAMP family in mice (). This unconventional LAMP-like protein defines a new endocytic compartment in specific subsets of cortical projection neurons. Interestingly, its post-natal expression coincides with cortical synaptogenesis, indicating a possible role in this process. Unlike other LAMP family members, BAD-LAMP has a highly restricted localisation: it is enriched in distinct intracellular vesicles in defined zones along the neuronal projections. Although BAD-LAMP is endocytosed, the vesicles in which it accumulates do not contain markers for classical intracellular transport pathways. Further analysis of BAD-LAMP endocytosis in HeLa cells revealed that it constantly recycles to the plasma membrane via a dynamin/AP2-dependent mechanism. The defined expression and distribution patterns of BAD-LAMP demonstrate a role for non-conventional endocytic vesicles and membrane lipids in the maturation or function of specific cortical neurones.
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