Physio-pathological roles of transglutaminase-catalyzed reactions

Table 1 TG enzymes and their biological functions when known

TG	Physiological role	Gene map location	Ref.
Factor XIIIa	Blood clotting	6p24-25	[15]
TG1 (Keratinocyte TG, kTG)	Skin differentiation	14q11.2	[16]
TG2 (Tissue TG, tTG, cTG)	Apoptosis, cell adhesion, signal transduction	20q11-12	[17]
TG3 (Epidermal TG, eTG)	Hair follicle differentiation	20p11.2	[18]
TG4 (Prostate TG, pTG)	Suppression of sperm immunogenicity	3q21-2	[19]
TG5 (TG X)	Epidermal differentiation	15q15.2	[20]
TG6 (TG Y)	Unknown function	20p13	[20]
TG7 (TG Z)	Unknown function	15q15.2	[20]

TG: Transglutaminases.

Table 2 List of polyglutamine (CAG-expansion) diseases

Disease	Sites of neuropathology	CAG triplet number		Gene product (Intracellular localization of protein deposits)	Ref.
		Normal	Disease
Corea major or HD	Striatum (medium spiny neurons) and cortex in late stage	6-35	36-121	Huntingtin (n, c)	[44]
SCA1	Cerebellar cortex (Purkinje cells), dentate nucleus and brain stem	6-39	40-81	Ataxin-1 (n, c)	[45]
SCA2	Cerebellum, pontine nuclei, substantia nigra	15-29	35-64	Ataxin-2 (c)	[46]
SCA3 or MJD	Substantia nigra, globus pallidus, pontine nucleus, cerebellar cortex	13-42	61-84	Ataxin-3 (c)	[47]
SCA6	Cerebellar and mild brainstem atrophy	4-18	21-30	Calcium channel	[48]
				Subunit (a1A) (m)
SCA7	Photoreceptor and bipolar cells, cerebellar cortex, brainstem	7-17	37-130	Ataxin-7 (n)	[49]
SCA12	Cortical, cerebellar atrophy	7-32	41-78	Brain specific regulatory subunit of protein phosphatase PP2A (?)	[50]
SCA17	Gliosis and neuronal loss in the Purkinje cell layer	29-42	46-63	TATA-binding protein (TBP) (n)	[51]
SBMA or Kennedy disease	Motor neurons (anterior horn cells, bulbar neurons) and dorsal root ganglia	11-34	40-62	Androgen receptor (n, c)	[52]
DRPLA	Globus pallidus, dentato-rubral and subthalamic nucleus	7-35	49-88	Atrophin (n, c)	[53]

HD: Huntington’s disease; SCA: Spinocerebellar ataxia; MJD: Machado-Joseph disease; SBMA: Spinobulbar muscular atrophy; DRPLA: Dentatorubral-pallidoluysian atrophy; c: Cytosolic; m: Transmembrane; n: Nuclear.