CALR and obesity due to melanocortin 4 receptor deficiency: We also found that cathepsin B (Ctsb), a lysosomal cysteine protease involved in protein turnover and proteolytic processing of amyloid precursor protein (APP), interacted with obesity- and feeding behavior-related proteins Calr, App, Hsp90ab1, Timp1, and Timp2 and inflammation-related Hmgb1 and Grn (Figure 5).