RPSA is required for the assembly and/or stability of the 40S ribosomal subunit. RPSA is required for the processing of the 20S rRNA-precursor to mature 18S rRNA in a late step of the maturation of 40S ribosomal subunits. RPSA also functions as a cell surface receptor for laminin and plays a role in cell adhesion to the basement membrane and in the consequent activation of signaling transduction pathways. RPSA may play a role in cell fate determination and tissue morphogenesis. It acts as a PPP1R16B-dependent substrate of PPP1CA [taken from the Universal Protein Resource (UniProt) www.uniprot.org/uniprot/P08865].