CNP-53

Where it comes from

Made in

Endothelium and brain; the main form stored in tissue

Sent out by

Cut to CNP-22 in or near the cell; CNP-53 itself is the tissue form

Acts on

• Vascular smooth muscle
• Chondrocytes
• Brain

What it does

• Binds and activates NPR-B as CNP-22 does; the extra residues at the front change its reach, not its message ¹
• The main form actually stored: in human hypothalamus and brainstem most of the CNP present is CNP-53, with CNP-22 a minor component ²
• Cut down to CNP-22 around the time of secretion, so what a tissue holds and what reaches a receptor need not be the same molecule ¹

In medicine

• No test and no medicine tells it from CNP-22: the assays in use see the shared ring at the C-terminus and report both together ²
• Vosoritide and navepegritide are built on CNP-22, so nothing in the clinic is aimed at the long form
• Its length matters to a laboratory rather than to a patient. A 53-residue peptide behaves differently in an assay, which is part of why reported CNP concentrations disagree between methods ²

Beyond the body’s own use

• It was found by asking what the antibodies raised against CNP-22 were really binding in brain extracts, first in pig and then in human tissue; that is still the only reason anyone measures it ¹
• What is genuinely unsettled is how much of the CNP in blood and spinal fluid is this form, and whether a tissue ever releases CNP-53 intact; the answer shifts with the antibody used ²
• No trial, no analogue and no claim attaches to CNP-53 itself