BACE1 and Alzheimer disease: Broad applicability of hiSPECS and the resource is demonstrated (i) by gaining new insights into the extent of cell type‐specific protein secretion and shedding; (ii) by identifying new substrates for the protease BACE1, a major drug target in AD; (iii) by determining the cellular origin of proteins in CSF; and (iv) by revealing that LPS‐induced inflammatory conditions in organotypic brain slices do not only lead to inflammatory protein secretion from microglia, but instead induce to a systemic secretory response from multiple cell types in brain slices.