Papilin is an extracellular matrix glycoprotein that we have found to be 
involved in, (1) thin matrix layers during gastrulation, (2) matrix associated 
with wandering, phagocytic hemocytes, (3) basement membranes and (4) 
space-filling matrix during Drosophila development. Determination of its cDNA 
sequence led to the identification of Caenorhabditis and mammalian papilins. A 
distinctly conserved 'papilin cassette' of domains at the amino-end of papilins 
is also the carboxyl-end of the ADAMTS subgroup of secreted, matrix-associated 
metalloproteinases; this cassette contains one thrombospondin type 1 (TSR) 
domain, a specific cysteine-rich domain and several partial TSR domains. In 
vitro, papilin non-competitively inhibits procollagen N-proteinase, an ADAMTS 
metalloproteinase. Inhibiting papilin synthesis in Drosophila or Caenorhabditis 
causes defective cell arrangements and embryonic death. Ectopic expression of 
papilin in Drosophila causes lethal abnormalities in muscle, Malpighian tubule 
and trachea formation. We suggest that papilin influences cell rearrangements 
and may modulate metalloproteinases during organogenesis.