Proprotein convertase subtilisin/kexin type 6 is an protease that in humans is encoded by the PCSK6 gene which is located in chromosome 15. [5] [6] Pcsk6 is a calcium-dependent serine endoprotease that catalyzes the post-translational modification of precursor proteins from its 'latent' form to the cleaved 'active' form. [5] Active Pcsk6 has been reported to process substrates such as transforming growth factor β, [7] pro-albumin, [8] von Willebrand factor, [9] and corin. [10] Clinically, Pcsk6 is suggested to play a role in left/right asymmetry, [11] structural asymmetry of the brain, [12] handedness, [13] [14] [15] tumor progression, [16] hemostasis, [9] [8] [7] and cardiovascular diseases. [10] [17]
The protein encoded by this gene belongs to the subtilisin-like proprotein convertase family. The members of this family are proprotein convertases that process latent precursor proteins into their biologically active products. This encoded protein is a calcium-dependent serine endoprotease that can cleave precursor protein at their paired basic amino acid processing sites. Some of its substrates are - transforming growth factor beta related proteins, [7] pro-albumin, [8] von Willebrand factor, [9] and corin. [10] Alternatively spliced transcript variants encoding different isoforms have been identified. [6]
During development: Throughout development, the spatial and temporal expression of pcsk6 regulates embryogenesis by activating TGFβ related differentiation factors, which include BMP and Nodal. [7] [18] Elevated levels of Pcsk6 was detected in maternal decidual cells of the implantation site and the extraembryonic ectoderm. [19] The regulation of proper gradient of Nodal and BMPs is crucial for gastrulation, [20] proximal-distal axis, [21] and establishment of left-right axis patterning. [22]
Developmental Pcsk6 knockout studies found that mice embryos that lack Pcsk6 develop heterotaxia, left pulmonary isomerism, and/or craniofacial malformations due to disruption in specification of anterior-posterior and left-right axis that resulted from the dysregulation of Nodal and BMP signaling. [11]
In humans, Pcsk6 VNTR polymorphism is associated with the structural asymmetry of the frontal and temporal lobe, [12] and degree of handedness. [13] [14]
Cardiovascular disease: Pcsk6 is increasing interest as indicator and factor of cardiovascular disease. Pcsk6 KO mice was shown to develop salt-sensitive hypertension due to failure of pro-corin activation crucial to atrial natriuretic peptide regulation of blood pressure. [10] A hypertensive patient was found to have a G/A mutation on the PCSK6 gene that resulted in an Asp282Asn (D282N) substitution at the Pcsk6 catalytic domain, which in turn, hinders corin processing. [10] In vascular remodeling, Pcsk6 was found to induce smooth muscle cell migration in response to PDGFB by activating MMP14. [17] When Pcsk6 was knocked out, the intimal hyperplasia response to in vivo carotid ligation was lowered. [17]
Other: This gene is thought to play a role in tumor progression. [6] [16]